Maltruant

Maltruant is a rogue, powerful and psychotic Chronosapien who sought the domination of time itself and the death of Ben Tennyson.

He serves as main antagonist of the Ben 10: Omniverse arc The Time War, and was voiced by Mark Hamill who is widely known for playing Luke Skywalker and The Joker.

Background
According to Professor Paradox, Maltruant is bent on ruling all of time and existence. For achieving such goal, he masterminded the past Time War. Fortunately, he was defeated by the end of this particular war. To ensure that he wouldn't be able to start another war and his followers wouldn't be able to find him and restored him, Paradox took him apart and hid the incapacitated individual parts of Maltruant's body throughout space and time. However, over time, Maltruant would slowly "pull himself back together," eventually reforming the majority of his body.

Personality
Maltraunt is portrayed as a intelligent, vain egomaniac who desires nothing less then eternal dominion over reality. Along with this he is shown to be a sadist who enjoys toying with enemies and even betraying a former allies once he no longer needed their help. He is known to brag once he feels he is about to win which has led to his own defeat before.