Writing Characters You Don't Like

I recently read The Thief by Meghan Whalen Turner. This story hooked me, even though during the first half of the book I didn’t particularly like the MC--he seemed to be always complaining. So what kept me reading? The story (especially the challenges the MC faced in trying to achieve his goal) and the interesting interplay of characters and personalities as the MC became friendly with his captors. The book was a satisfying read--and had an awesome, unexpected twist.

However, it made me think about the process of creating characters. For most of my characters, there’s something about them I like. For the ones I don’t, I tend to exaggerate what I perceive as “negative” qualities. I have a feeling that these more “negative” characters in my stories are not as fully realized as the others. Because I don’t like them, I find it harder to give them fully rounded personalities. Any thoughts or tips?