- Estimated achievement difficulty: 5/10
- Offline: 20 
- Online: 0
- Approximate amount of time to 400: 8-10 Hours
- Minimum number of playthroughs needed: 2
- Number of missable achievements: None [Level select available]
- Do cheat codes disable achievements: No cheats
- Does difficulty affect achievements: Yes
- Glitchy achievements: "Insta-Killed", "Speed Runner III"
- Unobtainable achievements: None
- Extra equipment needed: None
Welcome to Slender: The Arrival. Blue Isle Studios originally developed the game for PC, but it has now been ported over to Xbox Live Arcade with some additional content. You'll likely need to do three playthroughs of this game for all of the achievements, but luckily the entire game can be easily beaten in 45 minutes once you know what you're doing. There are some glitchy achievements, but none are unobtainable - any glitches can be counteracted.
Step 1: Normal Playthrough & Collectibles
First make sure your game is on normal difficulty in the options menu. Then, start the game. As you progress, you'll want to gather all of the collectibles so that they don't strain you on Hardcore or take your time on your Speed Runner playthroughs. For a video guide on collectibles, refer to The Collector II in the guide below. There are also several other miscellaneous achievements you'll want to gain on this run. They are:
- Level One ("Prologue"): "I Love Radio", "Master Pianist", and "Fearless Fun"
- Level Two ("The Eight Pages"): "I'll just take this, I guess?"
- Level Three ("Into the Abyss"): "Well At Least You Tried"
- The Last Level ("The Arrival"): "Tangled" and "Fire Proof"
- At your leisure: "Get Me Out of Here!" and "Why Am I Playing This Game?"
Step 2: Hardcore Playthrough
At this point, you should only be missing "Fearless" and the "Speed Runner" achievements. For your second playthrough, play on Hardcore difficulty (which unlocks upon completion of normal). Don't worry about collectibles, times, or anything else other than completing the levels, as the AI is very aggressive and your flashlight will run out.
The game is complete-able in two playthroughs if you get the "Speed Runner" achievements in this run or the previous one, but unless you have a lot of previous experience with the PC version of the game that is highly unlikely.
Step 3: Wrap-Up
Unless you missed some of the miscellaneous achievements from step one, you should only need the "Speed Runner" achievements now. Refer to the guide below for tips and videos on those.
If you've made it this far, congratulations on completing Slender: The Arrival!
[XBA would like to thank Neverender for this roadmap]