Superman.
I have to admit that I have never read the comics he is originally from. However, from what I have seen of him, he seems to be completely unstoppable, immune to everything, and unable to falter. This makes his stories boring and his victories meaningless because he has no problems to overcome and we never see him grow. He is not someone who inspires like Spider-Man or Captain America, and he is not someone who demonstrates ingenuity like Batman.
His origin story also doesn't make a whole lot of sense to me. The only place where his powers don't work is his native planet. You would think that the Kryptonians would have evolved to suit their planet better than Earth, but apparently the planet evolves with them. If that's the case, how is the planet alive? What does it have to gain by weakening the Kryptonians? And how is it that an inanimate shard of rock from that planet is enough to kill a kryptonian.
Anyway, that is my rant against the most popular superhero and the reason why it frustrates me when he takes center stage in anything DC related.