Bucky Barnes

James Buchanan "Bucky" Barnes was the teenage sidekick of Captain America in World War II. On their final mission, Bucky was thought to have been killed on an exploding plane, but he was actually found and brainwashed by KGB, being outfitted with a cybernetic arm to replace the one lost in the explosion, and used as their Winter Soldier, committing assassinations of political figures before being put back in suspended animation.

When the Winter Soldier came across Captain America in the modern day, his memories returned to him, and Bucky became Cap's ally once again. When Captain America apparently died, Bucky picked up the mantle himself, leading the Avengers through Norman Osborn's Dark Reign.

Bucky's death was faked so he could return to his life as the Winter Soldier, now secretly working for S.H.I.E.L.D.

Earth's Mightiest
Bucky, as Captain America at the time, eliminated Flatman in the opening round, before tying with Mockingbird. Bucky was moved into a Last-Chance Battle Royal to determine if he could make it into the finals tournament, but he was defeated by Daken.