*NOTE: Whoever is adding unregistered users for this game is clearly trying to sabotage my TA ratio. Seriously, stop. Or I will find out who you are and you won't like what'll happen next*
Whoo boy, this one is the BIG ONE. Unquestionably the hardest achievement in the game, and possibly one of the hardest (but still obtainable) achievements out there. Although I'm not the first to get this particular achievement, I am the first to complete the game, so I will try to explain in as much detail as I can how to get this one.
In order to get every costume, (every character has 4, 1 is unlocked at the start) you have to do 3 things, beat the game, get every level 3 weapon, and S rank every level.
Now, each character costume is tied to a difficulty. For example beating the game on thriller unlocks a new zach costume, while beating it on madness unlocks one for jennifer. All you have to do is beat madness to unlock all 4... good luck with that though. There is a pretty handy guide for that under the "Complete the game on madness" achievement though.
As for the weapons, this isn't tough but time consuming. Every character has to upgrade all weapons to level 3, and this means you have to play the game 4 times. You don't have to find those stupid melee weapons to unlock the costumes. More specifically, your looking at about 1.3 playthroughs/character to max out all weapons. I recommend Thriller difficulty for the best parts, or Horror difficulty if you are good. The Junkyard (level 5) is a good quick level to get a good amount of parts.
Then there are the S ranks. If you didn't know here is the criteria for an S rank.
- Collect X weapon parts (Self explanatory, these are all over the place)
- Collect X monster tokens (Self explanatory, blue tokens are worth 1, red is worth 5, and green is 10)
- Defeat X monsters (Specifically it's "get X score" but that's based on how many monsters you kill and how fast)
- Find your special melee weapon (Guide below)
- DONT DIE
In just about every level, all of these except not dying are fairly simple. I found a complete guide for the melee weapons if you can't find those. (http://forums.xbox.com/23062180/ShowPost.aspx
Not dying however is quite difficult, due to the game's high difficulty, and overabundance of glitches and poor controls. Doing this on madness is near impossible. You'll find luck is more of a factor than skill, you'll probably have to play a level more than once to S-rank it (Most a level took me personally was 5 tries)
Another hint is if you are going for the S-ranks, there are 2 main weapons you'll want at level 3: The minigun and the flashlight. I've finished levels (With S's) using only the minigun so it is possible. If you have specific weapons you like to use feel free to do so, just be sure they are level 3 AND hotkey'd to the d-pad.
Also a minor detail here, but the only levels that gave me any real trouble (ie. took more than 3 tries) were levels 4, (Downtown, that damned vehicle sequence) 14, (Catacombs, ALWAYS died on the minecart or at the boss. Hint; use the turrets at the boss to distract the other enemies) and level 18. (This level is just flatout nuts. No tips here, just be steady and calm... and possibly praise the heavens if you succeed)
There is a reason the average gamerscore for this is so low. (I believe it's around 27/1000) This achievement as you can see is borderline insane, and not worth the effort, not for any completionists, gamerscore whores, or.. ANYONE! I did this so you don't have to, but if you are hellbent on giving this a shot, i hope this guide gave you a feel for what you got yourself into, and please leave some feedback if this helped you or not.