Bruce Banner's father, Brian Banner, feared radiation. Soon, he believed his wife, Rebecca Banner was exposed to it. After Bruce was born, he was convinced he would become a monster. He tried to kill Banner, but killed Rebecca instead. So Bruce was sent to live with his aunt when his dad was sent to jail. In school Bruce was into learning about radiation. Eventually Bruce worked for a nuclear research program. Bruce's boss, Igor Starsky, was really a Russian spy. When the Gamma bomb was being tested a boy, Rick Jones (future sidekick of the Hulk) wandered into the sight. Bruce saved the boy, only to be affected by the radiation and turn into the Hulk. Soon he ended up beating up Igor. Although he was at first grey (and could lift 70 tons), he became green (and easily could lift 70 tons). First his transformation only took place when the sun set, later Bruce built a machine to control the change and finally the Hulk became free, when Bruce got mad. His rouge villain gallery include the hypnotic Ringmaster, the super smart Leader, the evil wizard Loki, Abomination and Madman (both have the Hulk's power, but stay smart), the psonic M.O.D.O.K and even some heroes like Thor, The Fantastic 4, Spider Man and the X-Men.
Incredible Hulk Ultimate Guide