Dr. Bruce Banner. Transformed into the Hulk after being exposed to a gamma bomb explosion while saving a teenager, Rick Jones, from the same blast. Banner is mild mannered and a pacifist while Hulk is consumed by anger. Banner doesn’t have control over when he is the Hulk and when he is himself. Banner has a genius level intelligence and while he is the Hulk is immensely strong and generally impervious to harm. Originally grey, Hulk is now green, usually wearing purple pants or trunks. Modern Jekyll & Hyde/Frankenstein.
Hulk repeatedly comes into conflict with his fellow Avengers and as a result leaves the team. (Avengers #2) The Avengers spend considerable effort attempting to bring Hulk back into the fold, if only to keep his unpredictable nature under control. Hulk has managed to evade this fate so far. (Avengers #3, Avengers #5, Avengers #17)