Amorbis
Discovered by
Prime Hunter
If you fire a charged light beam shot at him while in either form, it takes him out all of the way. Basically, if you hit him during the tunneling phase, it knocks off his armor entirely, instead of having to pump missiles and charged power beams into him. Then, when he's attatched to the ball, if you hit him again the armor on his head is destroyed, immediately letting you get inside him. (The whole sucking you in sequence) Use a normal bomb to blow him up while inside.
If I counted right, you can eliminate Amorbis completely with about 60 light beam ammo, if you hit every single time with the charged shot. You may need to hit him more if your shots aren't entirely accurate.
If you are having trouble, stay in the light crystal areas and watch the dirt trails.