Funny thing, had banners life not sucked so badly growing up, its entirely possible that explosion would have turned HIM into The Leader. Basically multiplying his intellect and mental abilities many fold. Imagine Banner being turned into something so smart that he could honestly consider reed and doom to be amateur dabblers in the field of science? Though that banner I dont see going evil. He would probably not be a hero either as he wasnt really the type to go heroing by choice. You could probably justify him going either way due to his intellect. He could be like movie ultron and decide the only way to keep humanity safe is to destroy the people (heroes included) endangering it with their actions. Or become a hero because he can nearly doc manhatten himself and predict how things will go so he steps in to stop the bad stuff.