HOW TO BEAT CRAWMERAX WITH ANY 2 PLAYERS. Including splitscreen with using 2 controllers.
I was tired of seeing that you had to have a siren or two hunters or four level 61 players to beat this guy, so I went out and looked up this method and added a few things to it. Most of the credit needs to go to HaloHunter72 and the glitch's originator HelterSkelter. Also I want to thank Katiahnya for the screen shot of where you need to stand.
First you will need a reasonably powerful sniper, (nothing huge) or a very accurate scoped weapon. Also you will need a smg, assault rifle, sniper or anything with a scope that can REGENERATE ammo (higher the fire rate the better)...or for soldiers and hunters a class mod.
Once you have your weapons set you and your other player go to the elevator to Crawmerax. One person goes up and the other decoy stays at the bottom of the elevator. Now facing forward move to the left closest angle to the front of the elevator and head on up to Crawmerax. As soon as the elevator gets to the top RUN LEFT to the ledge and DUCK DOWN (crouch) against the wall.
Link to a screen shot of where to stand to freeze glitch Crawmerax posted by Katiahnya
over in the Gearbox Forums
Only crouching enables the glitch and this does take a few tries each time to get Crawmerax to freeze glitch, it doesn't work every time.
In this spot Crawmerax will glitch and freeze and not attack you nor will his little worm buddies. He will sit there and roar over and over while you shoot all of his critical points. (This does take awhile depending on your level and how proficient you are with your gun the regens ammo) You will eventually blow off his 4 arms and pop his eye, but you have no angle to shoot the weak spots on his back and if you move you WILL die. Now here comes the decoy's job. Player 2 that was waiting at the bottom of the elevator comes up the elevator and Crawmerax will turn to attack him exposing his rear weak points to you. Make sure to stay DOWN and crouched in the glitched spot and snipe or aim well with your long range weapons and crit his rear weak point. (when the other player comes up you are no longer safe while he is alive so stay where you are.) If your partner dies and you stay in the glitched spot Crawmerax should not attack you and turn to face you and start roaring again and all his buddies should freeze. (make sure your decoy does not run towards you, have him run to the right when he leaves the elevator. Rinse and repeat with your decoy coming up the elevator and you sniping the final weak spot. When he pops enjoy the achievement and the massive amount of loot he drops.
(((Again I cannot stress this enough... if your decoy or decoys are just downed and dying you are still VULNERABLE even in the glitched spot, take you shots quickly and have your decoys force respawn by pressing X. Most of the time Crawmerax will go back to being freeze glitched.)))
This tactic is a great way to farm legendary and pearl weapons on either playthrough. I also recommend if you do have more than one decoy this would be easier. Just have the one player go up and freeze glitch Cramerax and once only the rear weak point is left bring up the rest of your team and crush him, but keep the one guy in the glitch spot just in case.
Finally I did this as a lvl 61 Berserker using a scoped ammo regen smg that had about a 30% increased fire rate... (it really wasn't that powerful of a gun and I found it in the knoxx armory on playthrough 1) and a legendary orion sniper for the final rear critical point it did about 900 damage a shot even though my sniper proficiency is only a level 9, my partner was a level 52 hunter THANKS Anaxaminder !!!!
DOING THIS ALONE via SPLITSCREEN is just a matter of timing.
If you decide to try this you can use any two characters still but I recommend your decoy be a soldier so you can level him up to about a lvl31 ish and equip soldier class mods that team regen ammo just in case you haven't found any regen ammo guns. (Do any leveling in the knoxx DLC because it goes super fast, or (SPOILERS) the area near the vault with all the guardians.
Splitscreen works the same as the solution above except when you send your decoy up make sure to keep your main character in the glitch spot and take a quick shot maybe 2 or 3 depending on your long range fire rate, then RESPAWN your decoy quickly because Crawmerax will turn on you even if your decoy is just downed. Once you force respawn the decoy as long as you in the glitched spot Crawmerax will re freeze glitch and you can rinse repeat.