They're two steps to defeating him. (first step) Take out a ranged weapon and start shooting him. (You should use a weak one cause its harder in the second step). (step 2) When his life is
about 1/4th down, you get taken into the strange space area. Take out a stronger weapon. A good way to get his life down is to you weapons that keep inflicting dammage even if you switch a weapon. (Example) If you get your weapon that launches tornados up to it's highest level, use that and take out another weapon to inflict lots of dammage. Also a really affective
weapon is the groovation device. At the side of the arena they're crates and life.