Hulk

Bruce Banner

Played by Mark Ruffalo

Bruce Banner is a physicist whose experiment with gamma radiation, intended to recreate the Super Soldier process, instead left him able to transform into the Hulk — a green, near-invulnerable giant of near-limitless rage and strength. He spent years suppressing and fleeing the transformation before learning to merge his own intellect with the Hulk's power, becoming a founding member of the Avengers and one of the team's primary sources of raw physical force. Read more →

First turns up in The Incredible Hulk.