Ultimos

Ultimos is the leader of the Galactic Enforcers and the most powerful hero on planet T-K. He first appears in The Galactic Enforcers. Ultimos reappears at the beginning sequence of Vengeance of Vilgax.

Powers and Abilities
Ultimos' powers are enhanced strength and durability, flight, heat vision and ice breath. He is very similar to Superman in terms of his powers, appearance and attitude.

Vilgax stole Ultimos' powers in Vengeance of Vilgax: Part 1.

In Ben 10,000, Ultimos still has his powers, but this is in an alternate timeline, meaning that Vilgax never stole his powers or he did and Ultimos recovered.

Weakness
Ultimos's weakness is chocolate. It turns his skin to a brownish gray color, makes him cold, shiver and collapse, and becomes skinnier when eaten. Synaptak identified that a specific chemical in chocolate is poisonous to Ultimos and his species.

Original Series
Ultimos showed up in The Galactic Enforcers to help Ben defeat Sixsix.

Alien Force
In Vengeance of Vilgax: Part 1, Ultimos lost his powers to Vilgax after he was defeated by the latter.

Ben 10

 * The Galactic Enforcers (first appearance)
 * Ben 10,000 (alternate timeline)

Ben 10: Alien Force

 * Vengeance of Vilgax: Part 1 (first reappearance)

Trivia

 * In Vengeance of Vilgax: Part 1, Vilgax called him "Ultimo".
 * Ultimos can be associated with Superman in various ways. He has enhanced strength, heat vision, super breath, flight and a "kryptonite", which is a chemical in chocolate.
 * It is unknown if Ultimos survived when Vilgax stole his powers.