Aside from the bullies picking on his pal Rogers, Barnes' first real enemies were the Nazis and the Nazi science division known as HYDRA. In particular, the HYDRA scientist Arnim Zola who turned Barnes into the Winter Soldier earns his enmity.
The Winter Soldier Program was a top secret HYDRA project started by Arnim Zola in the 1940s to brainwash American soldier James "Bucky" Barnes, whom he had administered with his own version of the Super Soldier Serum, and turn him into a super soldier assassin known as the Winter Soldier.
Once Hydra became more brazenly public in its operations, this led to the creation of the original agency known as S.H.I.E.L.D., specifically to counter Hydra's threat to world security.
Bucky Barnes spent decades as HYDRA's brainwashed Winter Soldier before an encounter with Steve Rogers and the Avengers helped him begin breaking out of their hold. He couldn't undo all their training on his own, however, and finally found true freedom thanks to Shuri's work in Wakanda.
While it is suspected that Hydra originated thousands of years ago in ancient Egypt, the modern-day organization was founded during World War II by Nazi agent Wolfgang von Strucker.
Johann Schmidt – the leader of Hydra, a special weapons division of the Nazi Schutzstaffel and a modern-day incarnation of the ancient society. Arnim Zola – a Swiss-born scientist working for Hydra before, during, and after World War II.
Different branches of Hydra were created since then, but the biggest one was created by Red Skull as the technology arm of the WWII Nazi party, and that branch went on to evolve after that while hiding within SHIELD.
We see that he's deprogrammed 6 months before the snap in FATWS. He's then snapped away and comes back 5 years later. FATWS takes place 6 months after he comes back. So Bucky is likely 33 physically while chronologically being 107 (FATWS takes place in April 2024, so Bucky's wrong about being 106).
Captured by HYDRA, Bucky Barnes was taken to the Siberian HYDRA facility where Arnim Zola replaced his missing limb with a prosthetic arm and turned him into a HYDRA assassin. For the next several decades, Barnes was activated to assassinate anyone who posed a threat to HYDRA.
Bucky was captured by Hydra in 1945, received experimentation with a variant of the Super-Soldier Serum, was brainwashed, and was implanted with a metal arm made of titanium to replace the left arm that was amputated when he fell from a train and plummeted nearly to his death.
After its defeat at the hands of Captain America in 1945 and the subsequent disappearance of Johann Schmidt, HYDRA was secretly rebuilt inside S.H.I.E.L.D. by Schmidt's top scientist Arnim Zola, who was recruited into the agency during Operation Paperclip and also formed an alliance with the Soviet Union.
Once again, the tentacles on the logo have a lot of meaning. They were inspired by the Inhumans' true form and the spaces between them resemble gears but they also remind the viewer of Hydra's heads. Just think about it: Hydra has long necks and heads sitting at their tips.
Bucky Barnes, like Steve Rogers, has lived for several decades due to cryogenic freezing and the super-soldier serum. Bucky's life expectancy could potentially surpass Steve's 116 years, depending on circumstances. Despite outwardly aging at the same rate as Steve, Bucky can still live for at least another 80 years.
The consensus seems to be that if we're just going by serum quality, Steve takes the cake (Zola's version wasn't quite as good as Erskine's formula), but Bucky's metal arm makes up the difference as far as strength is concerned. So, in that regard, they're roughly equivalent.
However, Barnes actually survived the fall thanks to the experimentation Zola had performed on him, and it was HYDRA who would make use of the man who would come to be known as the Winter Soldier...
How did the Hydra scientists brainwash Bucky Barnes into becoming the Winter Soldier? It's implied that HYDRA uses the same brainwashing techniques as Johann Fenhoff (Doctor Faustus) from Agent Carter. The ending scene from Agent Carter season 1 when Arnim Zola introduces himself to Fenhoff.
The fact that Bucky did wear the arm is why it disappeared according to the Russo brothers (via Comicbook), as they stated anything that was part of someone's identity would disappear when snapped.
After being captured by Hydra, Cap rescued him from being tortured. Even though he was shocked by Cap's new “look,” he still trusted his best friend and followed him to their escape. Loyal to a fault, Bucky joined Cap's Howling Commandos and fought bravely throughout Europe, taking down Hydra base after Hydra base.
Even Bucky's variant serum should allow him to age normally (unless he gets frozen again). A side effect of the Super-Soldier Serum that the Winter Soldier shares with Captain America is that neither can get drunk.
Unlike some characters, Bucky does have a canonical birthday: March 10, 1917. He's a little more than a year older than Steve, which makes him the oldest human Avenger at a chronological 106-years-old.
Surviving the war and believing Rogers had died during his last mission, Bucky eventually married Rogers' fiancé, Peggy and had two children, Marvin and Rebecca.
Thanos would dominate the Red Skull in just about every scenario. While Johann Schmidt may have the advantage in a scenario where he has a Cosmic Cube or Kobik and Thanos has nothing to counter it, even then Thanos would likely find a way to win the day.
Red Skull was cursed to become the guardian of the Soul Stone for over seven decades, rendering him unable to leave the planet throughout these years, only able to advise those who came onto the planet seeking the Soul Stone.
Debuting in Avengers #123, Vormir as a concept was created by Steve Englehart and William Robert Brown. There, the alien planet was the home of the Vorms, an alien race that heavily resembled gigantic dragons and lizards from the myths of Earth.
