BuckyReal Name: James "Bucky" Barnes

 Bucky was Captain America's partner during World War II, and expert in infiltration. He was apparently killed when the Red Skull's escape rocket exploded.

When Captain America touches the Cosmic Cube while fighting Baron Von Strucker, the energy of the Cosmic Cube apparently saves Bucky's life, and he falls into the water, injured but not dead.

Found by Hydra, Hydra scientists heal him and replace his damaged arm with a cybernetic replacement.  The Red Skull then brainwashes him, training him to be the Red Skull's personal assassin and operative, re-naming him the Winter Soldier.  Over the following decades the Red Skull will deploy the Winter Soldier to do his bidding, putting him in hibernation between missions so as to preserve his usefulness.

As the Winter Soldier, Bucky becomes part of the Red Skull's "Code Red" team, along with the Falcon, Doc Sampson, and the Red Hulk.  However, when the Red Skull orders the Winter Soldier to execute Captain America, his conditioning breaks and he injects Captain America with an antidote to the Red Dust bioweapon the Red Skull deployed on the Avengers Mansion.

The Winter Soldier is now at least mostly free of the Red Skull's conditioning.

Hydra Scientists turning Bucky Into The Winter Soldier