Is Superman the world's greatest superhero? That's up for debate, but he's almost certainly the most iconic. Even people who have never picked up a comic book know what that "S" symbol represents, and with history about to be made as the Man of Steel meets Batman on the big screen for the very first time, 2016 is going to be possibly his biggest year ever. Not quite so recognisable are the majority of the character's enemies. While there are a few which pretty much anyone should be able to name (mostly due to their live-action appearances), there are plenty who even some die hard comic book fans may have forgotten about. However, they all have one thing in common, and that's the fact that they're all great. Some might argue that heroes like Batman and Spider-Man have the best bad guys, but Superman can definitely give them a run for their money, and this lot are so powerful - let's face it, they need to be to take on the Man of Tomorrow - that The Joker and Green Goblin wouldn't stand a chance against them! So, from alien warlords to humans with a chip on their shoulder and near unstoppable monsters, these are the greatest Superman villains in comic book history.
15. Kryptonite Man
Yes, there really is a villain called Kryptonite Man in the DC Universe, and there have actually been SIX versions over the decades. They've all been portrayed in very different ways, but the fact that these guys are always powered by Kryptonite obviously makes Superman extremely vulnerable when battling it out with them. Why doesn't Kryptonite Man rank higher then? Well, he's never really been all that difficult to take down! Take "The New 52" version of this villain. Stopped by Superman while he was beating his wife, a vengeful Clay Ramsay signed up for the mysterious "Project K-Man" experiment which gave him powers enhanced by Kryptonite. However, the then rookie Superman took him down with relative ease, so we may have to wait until the seventh version to see Kryptonite Man become a real threat. He shouldn't be underestimated though!