As a reader, I've always had difficulty rooting for a "bad guy" protagonist in fiction; very rarely do I find one I can stand - Westlake's Dortmunder character, mainly because he's a just a likeable/unlucky schlub; maybe Doc in Thompson's The Getaway, though offhand I can't think of why.
I'm currently stuck on this problem with a character in my latest short story. He's an interesting guy, a pretty intense fellow, but I can't find a reason for readers to really connect and agree to follow him through the story... Anybody have any advice?