54. Abomination

When you have a character built up to be as incredibly (forgive the term) strong as the Hulk, it becomes nearly impossible to give him a credible threat. Enter the Abomination - created, for all intents and purposes, as the evil version of the Hulk.

Emil Blonsky might have begun as a Cold War era Russian spy, but after he was exposed to Gamma Rays, he became the same kind of huge, green, impossibly strong creature as the Hulk, giving the Hulk his first true equal in battle. More so, Blonsky had a couple of notable apparent advantages the Hulk didn't have, including keeping his own intelligence and personality while transformed, and a "normal" strength level that was even greater than the Hulk.

Still, thanks to the old "madder the Hulk gets, the stronger the Hulk gets" rule, Abomination was on the losing side of most fights. But in recent years, his approach became more psychological and cunning. In one of the more direct and scarring attacks a comic book arch enemy has achieved in comics, Abomination killed Bruce Banner's wife, Betty - and framed Bruce in the process. While Bruce's innocence would eventually be revealed, Abomination's actions would have longtime repercussions.