Uriah the Hittite. His murder is probably the most scumbag-move in the bible.
I hadn't read the whole bible before I saw "Man in the Iron Mask" as a kid, but that part of the movie where DiCaprio's character pulls that same move as King David- it really stood out to me.
It was very difficult to not think of David as a scumbag for a long time... but when I think about the circumstances and the aftermath he had to live with, I suppose he paid the price.
I have no doubt Uriah has a good reward in heaven. I find it very interesting that his name is mentioned in the geneology of Jesus. It seems odd to bring up that detail in the middle of a Geneology.