Bucky Barnes

James Buchanan Barnes Junior, known as Bucky, served as Captain America's youthful sidekick during World War II. He was a skilled operative who often handled missions requiring a different approach than Captain America's public persona allowed.

Presumed dead for decades, Bucky was later revealed to have been brainwashed and transformed into the assassin known as the Winter Soldier. He eventually regained his identity and even briefly assumed the role of Captain America.