WW2 Captain America: The only known success in the government's super-soldier program, Captain America and his sidekick Bucky fought against the Axis and Chitauri forces for years before Captain America sacrificed himself to save Washington DC from annihilation.

SHIELD Agent: Run by General Ross and later General Nick Fury, S.H.I.E.L.D. is a clandestine military organization dedicated to creating or controlling the most powerful super-humans in the world, including the X-Men, Spider-Man and the Ultimates.