I see your point, but in this case "supposed to like" is quite apt, I didn't like Anakin at all in the first movie, in the second he became bearable. Also, I think knowing beforehand what was going to happen to him possibly made it harder to form an objective opinion on him.

Have you read Colleen McCullough's first man in rome series? In there Marius is a character that has probably come closest to me liking then disliking (that I can remember at least). I really liked him to begin with, but at the end he turned really brutal and nasty, and I liked him less at that point. Overall though, I still liked him, just felt saddened at what happened to him at the end, though possibly helped that author suggested at least that strokes are what caused him to go so nasty. Generally, if I can see reasons why a character goes bad, I tend to be more sympathetic to them.