24. The Nihilanth
Watch The Final Battle: Click Here
How To Beat Him: This is the stuff of nightmares. Moving up and down that hollow-sounding chamber like you're floating in a lava lamp and firing missiles into a fetus-like monster wil make you shudder. Then there are the teleportation balls that force you to clear four other rooms filled with aliens. Just be prepared to deal with some mild psychological trauma from fighting a giant flying baby with exposed brain lobes.