11. Batman
These two may be the closest of allies and essentially best friends, but there's a very good reason that a movie called Batman v Superman is being released this year. These two have fought countless times over the years, and while they've often been manipulated into battling each other, some stories - Injustice: Gods Among Us and The Dark Knight Returns for example - have gone as far as portraying them as enemies. The fact that Superman isn't willing to cross the line by killing Batman means that the Dark Knight has an advantage in their battles against his far more powerful foe, and he doesn't hesitate to exploit that. Whether it's with a Kryptonite ring or the use of some badass armour, Batman has come close to permanently putting the Man of Steel down many times, and that alone makes him one of Clark Kent's more formidable foes.