This is a huge question that I can't begin to do justice to here, but I can give you a place to start.
Faulkner's heroes/protagonists are often unlikeable, even despicable characters, but he presents them without apology and sometimes even with dignity. Abner Snopes in "Barn Burning" is one such character.
Snopes is as unlikeable as unlikeable gets. He abuses his family, looks for reasons to start his little wars, and burns barns to get back at people who wrong him, as he sees it. I don't think he possesses one obvious and normal positive character trait.
However, at the same time, Abner Snopes is a poor man's hero, one might say. He, in a sense, does what many powerless people would like to do, but don't. We are refined, we know better. Abner does it anyway.
Abner holds on to his dignity the only way he can. In his world (the South after the Civil War), he is dirt poor with few opportunities to improve his lot. He is powerless, as twentieth century thinkers realized most humans are in the face of overwhelming powerful economic and social forces. Dignity is in short supply, as they say, for modern man. But Abner will not give in. He will hold on to his dignity any way he can.
If you want ambiguity, Faulkner's your man, and "Barn Burning" is a good place to start.