Sergeant James Buchanan "Bucky" Barnes was a former soldier of the 107th Infantry Regiment and the childhood best friend of Steve Rogers. Barnes was conscripted and assigned to the 107th in 1942. His regiment was captured by the forces of HYDRA, but Barnes along with what remained of his regiment were rescued by Rogers, who had become Captain America during Barnes' military absence.
Joining forces in the continuing war, Barnes and Rogers formed the Howling Commandos to battle the Red Skull's forces. During an attempt to capture HYDRA scientist Arnim Zola, Barnes was caught in an ambush and plummeted from the HYDRA train, where he vanished and was then presumed to be deceased.
Real Name: James Buchanan Barnes
Species: Human (Cyborg)
Date of Birth: March 10, 1917
Portrayed by: Sebastian Stan
Unbeknownst to his team, Barnes had actually survived the attack on the train, albeit with the loss of his left arm. Brainwashed and armed with a new cybernetic limb, Barnes ultimately became an enhanced HYDRA operative known as the Winter Soldier.
Over the next several decades, he would eliminate anyone who posed a threat to HYDRA, including his former ally, Howard Stark as well as his wife Maria. Between his missions, Barnes would be put into a cryogenic stasis to preserve his longevity.
Over half a century later, when he was ordered by HYDRA's new leader Alexander Pierce to assassinate S.H.I.E.L.D. Director Nick Fury. The Winter Soldier was unexpectedly confronted by his old friend, Steve Rogers, triggering him to begin remembering his prior life before HYDRA.
In the wake of the Battle at the Triskelion, the Winter Soldier went on the run from HYDRA onto a mission to remember his past and end his long violent history. However, Barnes was then accused of causing a terrorist bombing, which claimed the life of T'Chaka, the King of Wakanda, among others.
As Black Panther sought revenge for his father's death, Barnes was soon saved by Captain America, sparking the Avengers Civil War as Tony Stark was sent to capture him. As it was revealed that Helmut Zemo had organized the Civil War, he revealed that Barnes had murdered Stark's parents years ago.
Having survived the latter's revenge, Barnes was then taken into Wakanda where he was allowed by T'Challa to be frozen until his mind could be cured of all HYDRA's mental programming.
Barnes gradually recovered with help from T'Challa's sister Shuri and was nicknamed White Wolf.
Once Wakanda had come under the threat of the Mad Titan, Thanos for harbouring the Vision, who was currently in possession of the Mind Stone, Barnes had joined T'Challa and the Avengers to help fight off the threat, receiving a new Vibranium arm.
Despite their best efforts, managing to kill all of Thanos's forces, when Thanos came to Wakanda personally, he effortlessly overpowered Barnes and all of the heroes and finally assembled all the Infinity Stones and become victorious, with the Winter Soldier being among all those who were disintegrated.