Winter Soldier (Marvel Cinematic Universe)

Winter Solider is friend of Captin America who become his enemy. He is also known as James 'Bucky' Barnes and is the deuteragonist of Captain America: The First Avenger. His role is reduced to the secondary antagonist in ''Captain America: The Winter Soldier. ''He was supposed to be the main antagonist of the film, but this was part a misinformation campaign to hide the true villain of the film.

Childhood
Bucky first saved Steve as children from bullies in oprhange and they become friends which means Bucky become Steven's protector.

Captain America: The First Avenger
Bucky is first seen in the film as a Seargent in the US Army. He sees Steve being beat up by a bully and comforts him after a brief confrontation. He takes Steve and two girls to a World of Tomorrow Exhibit and departs to be deployed. He is next seen where he is being held captive by HYDRA and stripped to a chair. Captain America rescues him, only to find himself meeting Johann Schmidt (Red Skull). Afterwards, Captain America recruits him as his second-in-command of the Howling Commandos team to square off against Red Skull's HYDRA henchmen and destroy every HYDRA base in the overseas area. He is last seen in this film when Captain America and his team are deployed to bring HYDRA scientist Arnim Zola into custody. When a HYDRA  goon fires at Bucky with the Captain's shield, he instead is sent on the side of the train. Before Captain America could save Bucky, he falls to his apparent death into an icy cold riverside.

Captain America: The Winter Soldier
To be added.

Trivia

 * he had some simlmarites of Storm Shadow (G.I. Joe Live Action)