The Hulk

Dr. Robert Bruce Banner is a renowned scientist in the fields of Biochemistry, Nuclear Physics, and Gamma Radiation. However, after a Gamma Radiation experiment went awry, the mild-mannered scientist found himself plagued with a peculiar condition. When angered or provoked, he would transform into the rage fueled and nearly mindless, green-skinned monster known as the Hulk.

Fearful of the damage that the Hulk could inflict, Dr. Banner chose to live a discreet life in remote parts of the world, working to cure the sick and help the poor while trying to elude those who would take advantage of his ability to change into the enormous, green menace.

When a mounting threat called for Banner's specialized scientific expertise, S.H.I.E.L.D. Director Nick Furyrecruited him, knowing full well that the incredible strength of Banner's alter ego, the Hulk, would be an additional asset to the Avengers. After the Avengers split up, he became good friends with Tony Stark and was also given the freedom to live in the world without being hunted down.