It's been bugging me all day. Logan kicks ass, but He-Man had the power of grayskull. Not sure of 'the force' can be classed as a superhero though.
Superman is too powerful. Kryptonite basically annoys him, and that's his only weakness. He's been stabbed by it, encased in it, tied down by it... Still wins. I would say if Superman wasn't worthy of Mjolnir, Thor might have him counted out by wedging it on his cape, though.
The Marvel stuff is kinda endless. If memory serves I think someone called "Beyonder" is at the top of the tree. But in the interests of knowing who we're talking about, let's go Deadpool.