9. The Leader
In a former life, the Leader went by the name Samuel Sterns. In this life, Sterns was an unremarkable individual. He dropped out of high school and seemed fated to live the life of an unskilled laborer. Sterns's only dream was to be more like his brother, Phillip, a well-regarded scientist.
When Sterns took a job at a chemical research facility in the Nevada desert, his life turned around. Like Bruce Banner, Sterns was accidentally exposed to a lethal dose of gamma radiation.
Why was he exposed to gamma radiation at a chemical plant, you ask? Who the hell knows? But, this is the Marvel Universe. Naturally, he was imbued with superpowers rather than withering away like a popsicle left in the sun.
Unlike Banner, it was Sterns's mind, not his body, that was supercharged. He became hyper-intelligent and began calling himself Leader. Now, sure once he became Leader he got up to some pretty nefarious business. This includes creating an army of plastic humanoids to take overthrow the US government and capturing Bruce Banner and experimenting on him.
At one point, Leader did, however, operate on The Hulk to save the latter's life. But, for the most part, Leader has remained unredeemable. If maybe, he ever recalled his humble beginnings, the Leader could use his intelligence for good rather than evil.