Skullblaster Master 15
Defeat 50 enemies with the SKULLBLASTER
You will get this weapon at the end of act 4 making it somewhat difficult to get 50 kills with both the SMG and the Shotgun equivalent. I chose to do this on the first playthrough and do the dentist achievements on the second playthrough but it is advised to pick one. Any kill shot with this gun will count even if you have damaged them with another gun first.
Nasty Headache 20
Perform 5 Head Shots in a row with any weapon except Big Boner
The easiest way to get this achievement is by getting the 5 headshots in a row during the chapter 1-1 tutorial mission before you pick your difficulty setting. You can get this on your first playthrough or during one of the subsequent ones when you are used to getting headshots on tier 1 demons. Aim right at the center of the Peak of the demon's forehead or slightly above his head as this will eliminate any stray shots generally hitting shoulders. You are allowed to miss shots BETWEEN headshots but you CANNOT
shoot other body parts. you can tell you got a headshot if the camera/time slows down into black and white and zooms in on the headpop.
The Puppeteer 30
Perform a Head Shot right after a Leg Mutilation when the enemy is flying back in the air
This will likely be one of the two most difficult ones for you. The best way to do this is to use the dentist as seen in this wonderful video posted on the forums by Ra1nKing HERE
Now That's a Big Fuckin' Gun 15
Defeat 40 enemies with the SKULLFEST 9000
You will pick up this upgrade in chapter 3-3. Nothing fancy to this just kill 40 demons. I chose to do this on the first playthrough and do the dentist achievements on the second playthrough but it is advised to pick one. Any kill shot with this gun will count even if you have damaged them with another gun first.
A Hole in your Head 20
Perform 5 headshots in a row with the BIG BONER
This achievement can only be completed in chapter 4-1 right after Johnson requests you make the phone calls. This will come fairly naturally as long as you are aiming for their head ( The Giant RED spot on their head). You should be trying to lead your target slightly and compensate slightly for the bounce in their walk by aiming ahead to where they will be, making this achievement very easy. If necessary feel free to quit game and reload the checkpoint to ensure you get this.
Orthodontic Pleasures 15
Defeat 50 enemies with THE DENTIST
You will pick up this upgrade in chapter 4-3. Nothing fancy to this just kill 50 demons. I chose to do this on the second playthrough and do the shotgun achievements on the first playthrough but it is advised to pick one. Any kill shot with this gun will count even if you have damaged them with another gun first.
Drunk in Public 10
Knock back 3 drinks in a row
You must Be missing health for this to count properly, you should for sure get this on your hard playthrough knocking multiple sake's back subsequently. If you would like this in playthrough 1 (lemon hunter) you can control the damage you take until you get low enough and then knock back three sake drinks to unlock this achievement.
Stingy Bastard 10
Save more than 300 White Gems in your inventory
Assuming you are following my guide and using the two farming spots you will get this in the grind for 999 white gems, otherwise you can get this by just not spending anything until you hit 300 white gems and then finally buying items. On easy it's quite simple to go through the game without buying anything in the first place.
High in Las Vegas 75
Recover all available Red Gems in the game.
This is worded improperly you don't need to collect all red gems you need to collect all red gem upgrades. There are 80 upgrades in all and it will require you to farm in order to get this achievement. You can find Aruwal's guide Here
to help in getting the other 39 gems available, he lists 38 but I always ended up getting 39. 8-9 may prove difficult as sometimes one of the demons can't be destroyed by the chandelier in the 3rd part of the tower ride.
For farming white gems
There are 2 good spots to farm white gems where you can get to 999 rather quickly and efficiently and 1 more not so great spot but a good early start.
firstly in chapter 2-1 just after red gem #4 and during #5 getting the strawberry you will be instructed to light shot a goat head to stop demons from spawning, if you don't shoot the head they will crawl over the fence allowing you to just continually shoot off legs and stomp enemies for white gems.
The second spot is at 3-2 Red gem #15 you will follow the story into the lake and will be forced to chase an object in the water, if you forego this and move left from the initial broken bridge towards gem #15 you can farm demons continuously. I found it best to Light shot stun them and perform finishers by hitting
which will also allow you to get the Trash 'em while they're out achievement with strong likelihood, as long as you don't continue to the right of the bridge they will continue to spawn.
The third spot would be at 4-3 red gem #22. Right after you cross the bookshelf you will fight a few ground crawlers and then be ambushed by an armored form of the shadow portal monsters you fought in the swamps. Whenever they attack if you just backup or evade roll they will miss and then Jump quickly backwards, if you hit them with the light shot stun WHILE they are jumping backwards you will knock them down. Immediately continue over to them and start stomping them using the
as long as you continue to stomp them they will produce white gems allowing you to cap at 999 again. Rarely it won't let you collect gems whilst stomping just stop stomping and knock him down again and it should work. Video can be seen Here
in xxthegodofwarx's post
Fire in the Hole! 15
Defeat 3 enemies at once using the Barrels of Light
This is most easily achieved in chapter 2-3. When you first come across the sushi lamp it will lead you into a tunnel with 3 demons with Barrels of light behind them. Shoot the barrels and this achievement is yours.
Fiesta Caliente! 30
Defeat 5 enemies at once using the Hot Boner
One of a few spots to pick this up is in chapter 4-3 Right after you go up from the ground floor of the book cases and the first introduction to the electric demons. you will fight 3 demons, then 2 demons. Next a wave of 5-6 demons will hop over a desk right next to a light barrel (this is also another great spot for Barrels of light
) If you charge a bomb right after the second set of baddies and plant it at the large group's feet you can blast all of them in one fell swoop. Another spot for this is at the end of chapter 3-3 A group of demons will stumble out of a cave as it explodes you can also use the charge shot here for an easy 5 kills.