If you die and respawn after blowing off a crystal he becomes invincible since all his health regenerates, but the crystals you gotta hit to damage him don't.
He only regenerates his crystals if you save, quit and reload the game. --- You're the stranger, ain'tcha? Are you looking for a nice, clean place to stay? Madam, I had a nice clean place to stay... and I left it, to come here.
the crystals on his legs AND head/torso/body are weak spots. i have killed him 9 times now total and never had a problem, granted it did take a minute on the first time to realize the ones on body where weak spots also. --- GT: Kmalding1045
Use Torgue guns. Those types of enemies will take damage regardless of where you shoot them, no aiming for weak spots required. --- "If there's grass on the field, have sex with it." - Confucius talking to George Washington on their honeymoon cruise in the Bahamas