-When one of his claws opens, shoot it repeatedly. Do not lock-on because you will probably hit a different part of his body. After he screams "No!" and flies into the air, destroy all his legs and his claws. Locking-on is once again not recommended. His mouth will then open when all his legs and claws are gone. Shoot it until he is dead. Note: Shooting the eyes can also be done because he attacks with them, but they eventually return after awhile.
-Select someone with a lot of bombs. As soon as you start, drop as many bombs as possible on the Death Crab. Go through the rings to get more whenever you run out. It is possibe to defeat the Death Crab in about one minute this way.