Onslaught

During a battle between the X-Men and Magneto's Acolytes, Professor X used his telepathic powers to shut down Magneto's mind. During the psionic contact, Magneto's anger, grief, and lust for vengeance entered Professor Xavier's consciousness combined with every long-suppressed negative feeling the professor had endured during the last 30 years. This aggregation resulted in a separate personality within Professor Xavier, the being known as Onslaught.

Onslaught held the entirety of the Marvel Universe in the palm of his hand, using the combined powers of Charles Xavier, Magneto, Nate Grey, and the dormant psychic abilities of Franklin Richards, son of Mr. Fantatstic and the Invisible Woman to destroy a world that hated and feared him for being different. It took the combined sacrifice of The Avengers and The Fantastic Four to finally dissolve the Onslaught persona.

2D Fighters
Onslaught defeated Kaede in the opening round, but was overtaken by Rose in round 2.