There is such a variety of superheroes to choose from. So how do we know which one is the best? Well I can't do a break-down of every single superhero in existence. However, I have picked 3 that I believe to be the most powerful (go figure they are all X-men...).
The first superhero I picked is Wolverine. He has sick metal claws that come out of his fists but the reason I chose him is because of his regenerative power. His ability to heal gun shots and other serious wounds in seconds is extremely useful. This makes him hard to fight because no matter how much you hurt him he easily recovers and then lashes back with his Adamantium claws.
My Second choice is Magneto. He has the power to manipulate metal however he chooses. His power may seem simple, but in reality his power to control metal is ridiculously powerful as demonstrated in X-Men Days of Future Past when he lifts an entire sports stadium without a sweat! His helmet also protects him from any mind control attempts. All that combined with the ability to levitate/fly Magneto should be feared by all.
My third choice is Quick Silver. Quick silver was highly under-rated until X-Men Days of Future Past came out. In the movie we get to see a full show of Quick Silver's power. He can run at speeds up to Mach 10 which makes him a little to fast for a normal humans reaction time (#obvioussarcasmisobvious). however X-Men Days of Future Past is not the only reason I chose Quick Silver. Vsauce 3 recently published a video explaining the effects of Quick Silver running past you. In the video you learn Quick Silver wouldn't even have to make contact to injure you severely.
In my opinion Magneto wins hands down. His power over metal has no real limitations. I mean common, this guy is ridiculous. Not every superhero/villain can lift an entire baseball stadium no sweat!