South Park: The Stick of Truth Achievement Guide & Road Map

South Park: The Stick of Truth
South Park: The Stick of Truth Achievement Guide

Overview
- Estimated achievement difficulty: 3/10
- Offline: 50 [1000]
- Online: 0 [0]
- Approximate amount of time to 1000: 15-20 hours
- Minimum number of playthroughs needed: 1, if proper planning is done [see below]
- Number of missable achievements: 24 [Achievements listed as missable in the guide are ones that, if not obtained during game progression, cannot be obtained once the game is completed, during post-story playing, since no New Game+ is available. A new playthrough must be started, or an older save file reloaded]
- Do cheat codes disable achievements? No known cheats
- Does difficulty affect achievements? No [difficulty can be lowered all the way without affecting any achievements]
- Glitchy achievements: No
- Unobtainable achievements? No
- Extra equipment needed? No

Introduction
South Park: The Stick Of Truth is the long-awaited South Park RPG from Matt Stone and Trey Parker, and developed by Obsidian. The game feels like you're in an episode of South Park from start to finish, not only because of the graphics but also because of the content. So if you're a South Park fan, you will love the layout of this game. Despite the short play-time of the game, there are a ton of collectibles to find and friends to make. The content of the game is hilariously vulgar, and the style of gameplay is that of an old-school, turn-based RPG.

Option 1: Everything in One Playthrough
If you plan everything out before this playthrough, it could potentially be your one and only playthrough for the full gamerscore. To accomplish this, these are the things you need to remember to do throughout your entire playthrough, along with the achievements related to each step:

1. Play as a Jew ("Are We Cool?")

2. Do not sell anything all game ("For The Hoarder")

3. Never end a battle while one of your allies is knocked out. Either revive them before you win the battle, or revert your save and try again. ("No Child Left Behind")

4. Follow the Missable Guide (linked), which details friends, outfits, and Chinpokomon that are missable along the way. Also be sure to follow the Friends Guide provided Here. ("More Popular Than John Lennon", "Chinpokolypse", "Full Arsenal", "Clothes Whore")

5. The following achievements are missable, since they can't be obtained after the story is completed, but can be done many times throughout the game: "Irritable Bowels", "Dragon Wrath", "Re-Buttal", and "Mastery". Be sure to read their descriptions and accomplish them at some point during your playthrough.

6. The following achievements are once-and-done missable achievements that must be acquired at a specific point in the game: "Acceptance", "Heisenberg", "Gingivitis", "Day Walker", "KKK Hero", "Elven Hero", "Perverted", "Too Far", "Truth To Power", "Inside Joke", "Face Hoff", "Outpatient" and "Two Girls, One Stick". Make sure to read their descriptions on how to accomplish them. See the list below on when to do them.

Here I have listed all of the achievements in Step 6 roughly in chronological order of when they're obtainable, along with the area you get them in, as well as the achievements in Step 5 of when the easiest place to get them is.

Day 1
Acceptance - Kupa Keep right at the start of the game
Heisenberg - Kenny's house during the Calling Banners mission, Tweak's recruitment
Gingivitis - School, first visit (first possible time to get this)
Day Walker - School, first visit
Irritable Bowels - Giggling Donkey, boss fight

Day 2
Gingivitis - School, second visit (second possible time to get this)
Dragon Wrath - School, second visit (at least 3 opportunities to get this)
KKK Hero - School, second visit
Elven Hero - School, second visit

Day 3
Perverted - Underpants Gnomes main story quest
Re-Buttal - Underpants Gnomes main story quest (2 battle opportunities to get this)
Too Far - Abortion Clinic
Truth To Power - Cave in Canada (Prime Minister location, who is the only missable person)
Inside Joke - Inside Mr. Slave (must complete his side quest first)
Face Hoff - Final boss battle (must get the nose job before going to Clyde's)
Two Girls, One Stick - Final boss battle
Outpatient - Final boss battle (must acquire Dire AIDS before going to Clyde's)

Option 2: Split Between Two Playthroughs
If you want to sit back and enjoy the game the first time through to avoid spoilers from achievement descriptions and collectible guides, I recommend that at the least, you should do your first playthrough without selling anything for the "For The Hoarder" achievement. That way, on your second playthrough you can sell all the junk and patches you don't want as you progress, allowing you to afford more consumables, making it easier to get No Child Left Behind and to afford all of the outfits from the vendors along the way. If you do sit back and enjoy the first playthrough, and then want to make the second playthrough as easy to get all of the achievements as possible, be sure to check out the suggested class builds Here.

Step 3: Conclusion
No matter how you tackle this game, unless you are constantly searching every room and every area of the game, you'll likely need to use a collectible guide to manage to collect everything the game has to offer without missing something and having to start all over again. Don't let that stop you from enjoying the great game that has been created here. If you're a fan of the series, you should enjoy the immense amount of references and Easter eggs throughout this game, as well as all of the hilarious dialogue throughout.

[XBA would like to thank Necrophage33 for this roadmap]

New Kid On The Block

15
Join the KKK.
(24)
Story-related. Cannot be missed.

This achievement unlocks after completing "The Bard" main story quest.
First Day in South Park

15
Spend one day in South Park.
(8)
This achievement unlocks after waking up on the second day (not after going to sleep on the first night), after completing the "Alien Abduction" main story quest.
Gingivitis

15
Let Gingers bite you 3 times without blocking.
(15)
*Missable*

This achievement must be obtained either during your first visit to the school, during the main story quest to free Craig, or during your second visit when you assault the school. During the first visit, numerous Gingers can be taken out with the environment, and the game will prompt you to do so. During the second visit, however, the Gingers will be zombies, and therefore much more likely to bite you (as opposed to ranged or weapon attacks), so it might be easier to farm this achievement during your second visit.

I recommend making a save as soon as you enter the school. Go through the school and every time you fight Gingers, let them attack and block each attack until they perform Ginger Bite. Don't block this attack. Let it happen 3 times to get the achievement, then revert your save so you don't waste any potions you might have used while waiting for Gingers to bite you.

NOTE that if a Ginger bites your ally instead of New Kid, this still counts toward the achievement.
Day Walker

15
Defeat the Boss Hall Monitor while wearing freckles.
(4)
*Missable*

At the end of your first visit to the school, you will fight the Boss Hall Monitor. The boss fight starts as soon as you use the Gold Key. You must have Freckles equipped before going into the fight. The easiest way to do this is to create a character at the beginning of the game with Freckles. Otherwise, Freckles can be looted while inside the school, just remember to equip them as soon as you find them so you have them on during the boss fight.
Made This for You

15
Fling a turd that you created at an enemy in combat.
(7)
First you must create a turd (looting one in the sewers doesn't count). This can be done in any bathroom. Go to a toilet and press to hop onto it. Then you'll have to mash to fill the meter before the timer runs out. If you successfully fill the meter, the turd will come out of you and into the toilet. Press again on the toilet to loot your turd. Now that you have a turd, in battle, go to your Items, and pick the turd, then pick an enemy to throw it at. This will Gross Out the enemy and will unlock the achievement immediately.
Are We Cool?

15
Find Jesus while playing as a Jew.
(7)
*Missable*

Firstly, you must select the Jew class at the beginning of the game to unlock this achievement. If you want to play as a different class, this achievement can be gotten almost right away, so no worries. Once you finish the tutorial and can leave Kupa Keep, pull up your map and head to City Hall. Talk to Father Maxi to start his side quest. Go to the Church and find Jesus, who is hiding behind a pew. Go back to Maxi to continue the quest. Return to the church one more time and this time Jesus is hiding behind the altar. The achievement will unlock, as well as giving you Jesus as a friend, and granting you his Summon ability.
Parkeologist

15
Open all garages in South Park.
(6)
Every house in the neighborhood has a garage. Some can be opened straight away, others require you to find a key. The key is normally looted from inside the house itself, if the garage is locked. The earliest you can unlock this achievement is after the main story takes you to Kyle's backyard. Once there, you now have access to loot his house and find his garage key. His garage is the last one you can open. Also, storage units need not be opened for this achievement.

Three other garages of note:
1. Jimmy's garage key must be looted inside his house either during the story quest or afterwards, from the hallway outside the bedrooms
2. The garage on the house next to Mr Slave's only cracks open partially (need shrink ability to enter), but this counts as it being opened
3. Don't forget about Token's house, since it is set back away from the rest of the residential area
For the Hoarder

15
Sell nothing the entire game.
(14)
*Missable*

Self explanatory. You can't sell any equipment, patches, or junk. Nothing. Simply avoid going to the "Sell" tab any time you're at a vendor. As soon as you beat the final boss this achievement will unlock.
Truth to Power

15
Fart on the Mayor, Father Maxi, Principal Vic, & Prime Minister.
(9)
*Missable*

Here is where each of the four people is located in the game. You need to fart on each one.

Mayor - in City Hall (NOTE you must use Cup A Fart for the fart to hit her)
Father Maxi - on a bench in front of City Hall
Principal Vic - in the Community Center (must progress in the story far enough)
Prime Minister - *missable* found in a cave in Canada. If you don't fart on him here, he's gone and you'll have to start all over

The achievement should unlock after farting on the Prime Minister. It is highly recommended to use the Cup A Fart on every person listed above to ensure that your farts count as hitting them.
Irritable Bowels

15
Shit your pants during a boss battle.
(15)
*Missable*

See "Pulling Mud" achievement description. Just repeat during a boss battle.

Alternatively, while fighting Jimmy, at some point he will likely use an attack called Brown Bomber. He will play the brown noise, and if you don't block, it will cause your mana meter to max out and you'll shit your pants, unlocking the achievement immediately.
Dog Whistle

15
Fart on a canine enemy while in Gnome form.
(12)
After you progress in the story, you'll unlock the ability to shrink to Gnome size. Now you must fart on a canine enemy. This can be done either before battle if you Cup A Fart, or after you've defeated them, then you can fart on their body. If you don't get it during the progress of the game, after you finish the game you can return to the woods to fight dogs, and fart on their bodies after you defeat them, or Cup A Fart without fighting, as shown in the video below.
Dragon Wrath

15
Hit 3 enemies with a single fart outside of combat.
(18)
*Missable*

This achievement description is misleading. You must use a single fart to knock out three enemies at once, not just hit three enemies with your fart. The best time to get this achievement is during your second visit to the school. By this time you will have learned the Sneaky Squeaker, which lets you lure enemies to a specific spot. There are at least 3 parts in the school during your second visit where you can lure 3 enemies together and then use the environment to knock them all out. The video below demonstrates one of the first opportunities in the school.
Just Saying Hi

15
Fart on each available buddy in the game.
(2)
You must fart on Cartman, Kenny, Butters, Kyle, Stan and Jimmy. Once you unlock them all, just switch to each buddy and fart on each one. The achievement will unlock after the sixth one.
Re-Buttal

15
Interrupt 5 channel attacks with a fart.
(23)
*Missable*

Enemies won't start channeling until after you finish your first visit to the school. The Boss Hall Monitor will channel at times, as will The Bard. Most notably, the Gnomes channel often. Each time an enemy channels, make sure you have enough Mana (you can use the basic fart spell for 40 Mana to count toward the achievement), then unleash a fart spell on the channeling enemy. It will interrupt their attack, cancelling it essentially, and will gross them out. This needs to be done 5 times cumulatively to unlock the achievement. I recommend making a save and then farming this on the Underpants Gnomes. Fill your Mana before battle (you'll battle 3-4 at once). When they channel, often more than one will channel on the same turn. If you've already maxed your Mana before battle, you can drink a Speed Potion, use Dragon Breath on one of the channeling gnomes, then use it again on one of the others. This will give you two in one turn.

If you don't have this achievement by the time you beat the game, another place to farm this is on Craig in Cylde's Tower. When he makes clones of himself, they will sometimes channel, although not as often as the gnomes, so try to get as many on the gnomes as possible.
Heisenberg

15
Defeat the Meth Tweekers while wearing the Evil Cartman goatee and the bald cap.
(20)
*Missable*

The goatee is located in Cartman's bedroom. Loot it from a dresser. The bald cap is in the bag in Romper Stomper's cell in the police station. You must go to the second floor, shoot open the vent, go into the locker room, loot the jail cell key, then unlock his cell and loot the bag. Make sure to equip both. You need to wear them before you go to Kenny's house during the Calling Banners main story quest to recruit Tweak. This is one of the first quests in the game, so make sure you go to the Police Station right away. After you defeat the Meth Tweekers, the achievement will unlock.
Shutout

15
Successfully block every enemy attack in a single, non-tutorial battle.
(5)
After you learn how to press to block in the tutorial, you can now get this achievement at any time. You must be attacked a minimum of one time by the enemy for this to count, so if you can fight as few enemies as possible, do as much damage as possible on your first turn while leaving one alive. Let him attack and make sure when you block it, you see a Perfect below your PP. Finish off the last enemy and you'll get the achievement after the battle is complete. I found this easiest on a set of 2 elves in the neighborhood. You should easily be able to kill one on your first turn, let the second one attack you and make sure to block it (their attacks are pretty basic and predictable), finish off the second elf and the achievement will unlock after the battle.
Stay Down

15
Fart on 10 enemies in the world when they're knocked out.
(1)
Each time you defeat an enemy, their body will remain knocked out on the ground until you leave the area. Be sure to fart (down on ) on each knocked out body before you leave, and you should have this achievement very early in the game. You'll know you farted on them if their body jumps and they react to it.
Avenger

15
Defeat at least 3 enemies in one battle while your buddy is unconscious.
(8)
NOTE that if you end a battle with your buddy unconscious, it will void the No Child Left Behind achievement.

You must be in a battle against at least 3 enemies. Let your buddy get knocked out while at least 3 enemies are still fighting, then knock them out by yourself. The easiest way to do this is to attack all 3 enemies until their health is very low, then let them knock out your buddy, then finish them off. I recommend making a save before doing this so as not to void the No Child Left Behind achievement.

The easiest places to do this are against the rats in Skeeters Bar, as they're very weak, or against a group of 3 kids in the neighborhood. To avoid killing the enemies, simply don't press or after you initiate a melee attack.

Tip: if you make Butters your buddy, enemies are more likely to attack him. That way, he'll take most of the damage and get knocked out quick, so you don't get frustrated with enemies constantly attacking you instead of your buddy.
No Child Left Behind

15
Complete the game without ever ending a combat with a buddy knocked out.
(27)
*Missable*

As the achievement says, throughout your entire playthrough, you must never finish a battle while a buddy is knocked out. If your buddy does get knocked out, you CAN revive him, just so long as the battle doesn't end while he is knocked out. As soon as you beat the final boss this achievement will unlock. I recommend making continual manual saves throughout your playthrough in case you walk into a battle you can't handle. If you do accidentally end a battle with a buddy knocked out, reload a previous save/checkpoint to avoid missing the achievement. Also remember that you can lower the difficulty in the Options menu at any time without affecting any of the achievements.

An important general combat tip: if you initiate a random fight (swing your weapon at the enemy to start a battle), this means you get to attack first! If the enemy comes up to you and strikes you to start combat, they get to attack first. So make sure you initiate the battles as often as possible, letting you attack first so you have the upper hand.

See the recommended class builds Here to help make your playthrough much easier.
Poco Chinpoko

15
Collect 5 Chinpokomon.
(1)
See "Chinpokolypse" achievement description.
Chinpoko loco

30
Collect 15 Chinpokomon.

See "Chinpokolypse" achievement description.
Chinpokolypse

75
Collect all the Chinpokomon.
(26)
There are 30 Chinpokomon scattered throughout the game, some of which are missable, as they are in areas of the game that you can't revisit after story quests.

Here is a guide to all 30 locations:

Follow the Missable Guide (linked) to ensure you get all the missable ones, and you can go back and collect the remaining ones at any time. Press and scroll over to the Collectibles tab to see which Chinpokomon you've collected.

One last back-up (thanks to Xerofox, via IGN)

Do Not Miss These Chinpokomon

If you miss these Chinpokomon, you will not get another chance, so be sure to look for them in the following missions (in order of appearance).
Roidrat - (The Bard) In the attic of the Giggling Donkey
Beetlebot - (Alien Abduction) On the UFO, shoot Beetlebot on the monitor in the room before the final boss
Gunrilla - (Gain New Allies) Shoot down Gunrilla from the top of a file cabinet in the government meeting room.
Pterdaken - (Attack the School) In a locker on the second floor of the school.
Fetuswami - (Forging Alliances) This is picked up next to the automatic turret gun in Unplanned Parenthood.
Shoe - (Beat Up Clyde) At the very top of Clyde's fort, use the anal probe to warp to it.
Daddy Issues

15
Befriend your Dad.
(18)
First you have to acquire at least 50 friends. Press , and on the home screen your friend count will be displayed in the lower left corner. Then go talk to your dad in your house and he will become your friend. Refer to This Post for a list of all 120 friends. You won't be able to obtain 50 friends until after you obtain the Probe ability.
More Popular Than Jesus

30
Befriend Half of South Park.
(5)
See "More Popular Than John Lennon" achievement description. You must acquire 60 friends for this achievement.
Junk Peddler

15
Sell 300 junk items.
(4)
You will acquire junk all throughout the game from looting bags, drawers, and knocked out enemies. If you loot all throughout your playthrough, you can get this very early in the game. NOTE that this achievement will void the For The Hoarder achievement. I recommend earning For The Hoarder first, and then selling your junk after you finish the game. While there is no New Game+, there is post-game play where you can sell all of your junk to obtain this achievement.
Ass of Fire

15
Kill 20 enemies with Cartman's ass.
(3)
Once Cartman becomes an available buddy, set him as your buddy. In battle, you must use one of his fart attacks to kill an enemy. Repeat this on 20 enemies cumulatively to unlock the achievement. His best fart attack is his ability on the right of the wheel. It is an AoE attack that hits all enemies with fire, meaining you're more likely to kill multiple enemies with this attack at once. You'll unlock Cartman while the zombies are still present, and this is the best time to farm this achievement, as a lot of zombies are weak to fire.
Canadian Handshake

15
Fart on people 100 times
(6)
This does NOT need to be done on 100 different people. This can be gotten on any conscious person. Just stand next to them and spam farts until the achievement unlocks. Press down on the to fart.
Animal Cruelty

15
Fart on animals 25 times.
(9)
This does NOT need to be done on 25 different animals, nor do the animals need to be enemies. This can be done in Kupa Keep on the fenced in cat, or on any cat around town. Just spam it with farts until the achievement unlocks.
Pulling Mud

15
Shit Your Pants in battle three times.
(9)
First, you need to unlock Mana, which you get after Cartman teaches you your first fart spell in Kupa Keep. Then you need to acquire some Mana potions. You can use the potions outside of battle to actually fill your meter. Then go into battle and you'll see your Mana meter flashing with a warning sign. This means one more mana potion will make you shit your pants. Eat the mana potion to shit your pants.

This achievement does not need to be done all 3 times in a single battle; it is cumulative. I recommend making a save and then doing it three times in a battle back-to-back to get the achievement, then reverting saves to avoid wasting the mana potions.
Shopaholic

15
Complete half of the available costume sets.
(1)
See "Full Arsenal" achievement description
Clothes Whore

75
Complete all available Costume Sets.
(13)
See "Full Arsenal" achievement description
Friends in Strange Places

15
Befriend Crab People and Underpants Gnomes.
(7)
To befriend the Underpants Gnomes, you must complete their side quest to find 5 pairs of underpants. The underpants can be collected at any time, however the sidequest with the Gnomes only becomes available after you finish the story quest related to them at the start of Day 3. The underpants are located:

1. In Cartman's room
2. In Stan's room
3. In Stan's parents' room
4. In Kevin Stoley's room
5. In Kyle's room (must progress in the story)

To befriend the Crab People, you must acquire the final fart spell, Nagasaki, from Terrence and Phillip in Canada, which is near the end of the game. Then you must go all the way to the end of the sewers (or enter next to the movie theater if you've opened that manhole) and break the rock with your Nagasaki. This will clear the path to the Crab Person, who will friend you after talking to him.
Weapon Proficiency

15
Score 100 perfect attacks.
(1)
In the tutorial, Cartman will teach you how to press (or ) during an attack when you see the glimmer to score a perfect attack. You have to do this 100 times during battles throughout your playthrough to unlock the achievement. You'll know you've done a perfect attack if you see a "Perfect" below your PP.
Skilled Defender

15
Block 100 attacks.
(1)
In the tutorial, Cartman will teach you how to press during an enemy attack when you see the marker to block the attack. You have to do this 100 times during battles throughout your playthrough to unlock the achievement. You'll know you've done a block if you see a "Perfect" below your PP.
You bastards!

15
Have Kenny Die 10 times in battle over the course of the game.
(9)
NOTE that this will void the No Child Left Behind achievement if you end a battle with Kenny dead.

The easiest way to do this is to finish the game (i.e. unlock No Child Left Behind first), then go to Canada with Kenny as your buddy. Use Kenny's Rat ability and don't move the control stick. This will automatically kill Kenny and damage all enemies. Finish the enemies off with your character. Repeat against all of the dire animals in Canada, enter the cave, exit the cave, and repeat until you've done it ten times.
Mastery

15
Unlock all the upgrades for one of the New Kid's abilities.
(2)
*Missable*

You must fully upgrade one of your 5 abilities to level 5 to unlock this achievement. You unlock an upgrade each time you level up. Be warned, the level cap is 15, so you have 15 upgrades to allot, over the 20 options. You can see all levels of each ability at any time though, so review each ability and see which one(s) look best for maxing out. Worst case, if you prefer to divy your upgrade points evenly amongst all abilities, you can save an upgrade or two and max out an ability for the achievement, then reload your previous save.
Make it Rain!

15
Spend $500.
(2)
This is cumulative over the entire game. If you're going for "Full Arsenal" you will easily spend this much money buying all the equipment. To amass this much money, make sure to loot everything along your playthrough, even taking all of the junk. You will also be given money for completing quests, so make sure to do as many side quests as possible. You also will find cash, junk and consumables on bodies after defeating enemies in battle, so be sure to loot their bodies. After unlocking "For The Hoarder", sell all your junk and you should have enough money to spend to reach the $500 mark.
Full Arsenal

15
Collect all the weapons and costumes available in the game.
(23)
*Missable*

You must acquire all 103 pieces of equipment/costumes. This can be viewed by pressing , then scroll over to the Collectibles tab, then scroll over to Equipment. Here you can see your status. The costume sets/equipment are acquired from a combination of looting them from drawers, bags, etc., looting them from knocked out bodies, getting them as quest rewards, and buying them from vendors. Note that, for example, the Witch Hat, Witch Robes and Witch Gloves do not count as 3 toward the 103 counter; you must collect all three pieces of a single costume to count as 1 toward the 103 counter, so don't be surprised if you collect a hat, robes or gloves and don't see your counter go up by 1.

Here is a list of all of the costume pieces and equipment you must acquire: https://www.videogamesblogger.com/2014/03/07/south-park-the-stick-of-truth-weapons-and-costumes-locations-guide.htm
(Full credit to the guys listed at the bottom of that guide for assembling this perfect list)

The equipment you can/must buy from vendors is NOT missable (you can return to every vendor post-game to buy everything they're selling), however some of the looted equipment is. Be sure to follow the Missable Guide (linked) to make sure you at least pick up all the missable equipment during your playthrough.

NOTE that you need not possess every piece of equipment simultaneously! In other words, you CAN sell old stuff to make money to buy new stuff. As long as you've possessed the equipment at some point, it will tick off on your equipment list.

If you still need money to afford everything after selling all of your useless stuff, refer to This Post for some money farming methods.
More Popular Than John Lennon

75
Befriend all of South Park.
(36)
*Missable*

This achievement requires you to acquire all 120 friends in the game, INCLUDING Clyde at the very beginning of the game, who is technically the 121st friend, but he removes you immediately after being banished. You must talk to Clyde right in the beginning of the game in Kupa Keep, before talking to Cartman, or you'll be unable to unlock this achievement even if you get all 120 friends.

Follow the Friends guide Here for a rough chronological list of all 121 friends. It also highlights which friends are missable. Also use the Missable Guide, which includes missable friends in each quest when they appear.

Keep in mind that while there is no New Game+ to get missable friends, there is post-game play where you can mop up some friends that you may have missed while playing (the un-missable friends), so if you aren't complete with the friends list by the time you finish the game, as long as you've gotten the missable friends, you can go back post-game and get the remaining ones to unlock this achievement.

KKK Hero

30
You defeated the High Jew Elf Kyle in battle.
(2)
*Missable*

See "Elven Hero" achievement description.
Elven Hero

30
You defeated the Grand Wizard Cartman in battle.
(2)
*Missable*

Create a save during your second visit to the school. At the end you will have to choose who to fight, either Kyle or Cartman. Fight one, then revert saves to fight the other, ensuring you get both achievements in one playthrough. Who you choose to fight has no impact on the game or any other achievements.
Nonconformist

15
You befriended the Goths, like everyone else playing this game.
(4)
Story-related. Cannot be missed.

You'll unlock this achievement after completing the main story quest "Befriend The Goths."
Inside Joke

15
While inside Mr. Slave, you summoned Mr. Slave.
(13)
*Missable*

First, you must acquire the Mr Slave summon. Go to the post office, and in the back behind the counter you'll find Mr Slave's package. Return it to him at his house and you'll unlock his summon. NOTE that you can only use him once per day, so make sure not to use him on the third day (the day that starts with the Underpants Gnomes). During a battle inside Mr Slave, use his summon to unlock the achievement immediately.
Face Hoff

15
You defeated Princess Kenny while looking like David Hasselhoff.
(15)
*Missable*

You must buy the Dave Hasselhoff nose job from Tom's Rhinoplasty before going to Clyde's house at the end of the game (right after befriending the girls). This will cost you $175. Then you must beat the game (Kenny) while "wearing" this nose job. If you don't want to have to waste $175 on this so you can spend it on equipment, create a save after you befriend the girls, get the nose job, finish the game and get the achievement, then revert saves so you don't have to waste the $175 and can spend it on equipment you need.

This should be paired with "Two Girls, One Stick" and "Outpatient" achievements. All three can be gotten simultaneously.
Acceptance

15
You accepted your fate and chose the name Douchebag yourself.
(4)
*Missable*

In the very beginning of the game, Cartman will ask you what your name is. No matter what you type in, Cartman will ask if your name is Douchebag. Respond "yes" both times and the achievement will unlock.
Two Girls, One Stick

15
You defeated Princess Kenny in your girl makeover disguise.
(9)
*Missable*

The disguise is acquired as part of the main story line. Equip all pieces of the disguise (there are 4) before the final fight, and you'll unlock the achievement after the battle is complete.

NOTE that you must remove your extra rings, gloves, facial hair and face paint or the achievement won't count. You must only be wearing the 4 pieces of this disguise.

This should be paired with "Face Hoff" and "Outpatient" to unlock all three achievements simultaneously.
Outpatient

15
You defeated Princess Kenny while living with Dire AIDS.
(16)
*Missable*

You can acquire Dire AIDS from the dire wolves or snakes in Canada. Let them attack you until the game tells you that you acquired it. Don't remove it at the clinic. Simply finish the game with it and you'll unlock the achievement. The Dire AIDS doesn't affect you outside of battle once you have it. In battle, however, you will lose some health after each turn. There have been reports that it will eventually be removed after a certain amount of time. I recommend making a save after Canada when you're ready to go to Clyde's fortress, letting a dire animal bite you to give you AIDS, then go finish the game.

This can be paired with "Face Hoff" and "Two Girls, One Stick" to get all three achievements simultaneously.
Perverted

15
You watched your parents have sex for 60 seconds.
(12)
*Missable*

During the sequence with the Underpants Gnomes during the main story, you'll come to a part where you're on your parents' dresser in their bedroom and they're having sex in bed. Simply face them in bed and sit idle for 60 seconds and watch until the achievement unlocks.
Stick Savior

25
You defeated Princess Kenny and recovered the Stick of Truth.
(2)
Story-related. Cannot be missed.

You'll get this after you beat the game. Defeating Princess Kenny is a long battle that involves fighting Kenny 4 times, so make sure you have plenty of potions. This is the last battle, so don't hesitate to use Speed Potions to get in extra attacks each turn, but remember that your potions need to last across four sets of health on Kenny.
Too Far

15
You farted on the corpse of an aborted Nazi Zombie fetus.
(7)
*Missable*

This must be gotten when the main story quest takes you into Unplanned Parenthood. After you fight a Nazi Zombie fetus (or kill it with the environment), make sure to fart on its corpse before proceeding, to unlock the achievement. If you forget to do this during the main quest, as long as you come back before you go to Clyde's, the boss's body will still be there to fart on and unlock the achievement.