This video shows you how to kill Crawmerax by yourself if you're not a Siren. If you're a Siren you can do this too but it might be easier for you to just kill him straight up. Basically, if you make it to this spot on the map quick enough he won't be able to "see" you so he won't attack or respond to any of your attacks so you can just chip away at his critical zones. You will need to have at least one gun that can ricochet bullets as you will need it to reach the critical spot on his back. If you reach this spot and he still attacks you then you will probably die very quickly and try again, sometimes he moves enough from his starting spot by the time that you get to the corner that he can see you. Also, not every time will his minions attack you but sometimes they will, like in this video, so make sure you have what you need to kill them.
If you don't have a gun that ricochets bullets you can use a Nidhogg or Mongol rocket launcher as well. Just aim over his back and let the secondary rockets fall down onto him.
Maggots: kill with shock damage Purple crabworms: kill with corrosive Green crabworms: kill with fire
Credit for glitch discovery goes to HelterSkelter67 on the xbox forums.
:::Extra important notes::: -The majority of guns that ricochet bullets are smgs. If an smg fires bullets in a spiral pattern, like this video, then it ricochets bullets -As of now it looks like only sirens can use a nidhogg to hit his back because they are able to increase the speed of the rockets, allowing them to travel all the way to his back before they explode. So if you're not a siren go for a mongol, not a nidhogg. -If this isn't working for you then you are probably doing something wrong. Make sure you immediately start running to the corner and stay close to the edge and wedge yourself into the corner when you get there and don't move