I can see this quickly becoming a bash thread, btw, so maybe you should make it so people should leave a detailed and somewhat sensical reasoning as to their choices.
Much like, say, the Yankees or Duke, Superman would get a lot of points for most liked but also most hated. It would be interesting to see if we could quantify the two types of lists to show who is actually the most liked based on negative points for being hated as well. It would be someone who is liked by a lot but hated by few.
I really don't dislike a whole lot of comic characters. Most of those I'm not a fan of, I just choose not to read/follow, but right now Sentry is probably my most disliked character. I don't really like how he was forced into decades of continuity and set up on a pedistal to be the most powerful/greatest hero the world ever known...only everyone forgot. He's basically a Gary Stu if I ever saw one and it doesn't help that his plot device powers alter drastically only to, y'know, further the plot.
I do find it somewhat amazing that a lot of people seem to hate Superman as a character, and some for the sole fact that he is Superman. TBH, I'm not his biggest supporter or anything, but it does seem he gets a lot of flack.
I do a pretty good job of not letting forum idiocy affect my personal opinions of characters, which is where a lot of votes against Sentry would likely come from right now. I can really only remember 2 characters that I've ever liked less as a result of KMC. Storm and Hulk...though I didn't really like them much before that either, so it didn't change much for me.
Superman's a symbol, so he'll take hate. Reading his books isn't really so bad. And I actually love the idea of his character and how DC explicitly tries to write their Big 3 in almost mythological terms. So I'd agree that some of it is just because he is who he is. Personally I'm surprised there aren't more Cap haters outside the US.
Though I never realized why I don't like Hawkman until you spelled it out there. Completely right. And Rulk should go without saying. Unless you have Rulk in your sig, this thread should be "most disliked besides Rulk."