The Red Skull is the mostly the nemesis of Captain America, starting in the World War II years. The Red Skull was a Hitler Nazi Gestapo SS Super Agent who fought against the allies time and time again until finally beaten by Captain America, Bucky and the Invaders ending with a final battle that left the Red Skull buried under the rubble of a bombed building (Exposed to an experimental gas as the building collapsed, the Red Skull remained there in suspended animation for decades).
The Red Skull was eventually rescued and revived from suspended animation in modern times by the terrorist organization known as HYDRA. Red Skull quickly subverted