Season 3, Episode 2 - "The Vengeance of Vilgax, Part 2"
11 September, 2009
Following the accident with the Omnitrix, Ben, Gwen and Kevin set out to recapture the four released forms: Chromastone, Goop, Spidermonkey, and Way Big. They are able to capture three of the four, but Way Big is too far away to reach in time. Ben leaves to fight Vilgax while Gwen and Kevin retrieve Way Big. The battle goes badly for Ben at first, as Vilgax's powers and wide array of weapons are able to overcome his various alien forms. When Gwen and Kevin return with Way Big, Ben attempts to use the form, only to end up as Chromastone instead. Vilgax overcomes Chromastone and destroys his body, but Ben regenerates from the remains into Diamondhead. Using Diamondhead, Ben easily defeats Vilgax. Vilgax is banished from Earth and never allowed to return, but promises to get his revenge somehow.
