We can have the final word on hate, neglect, disease and all the other insidious characters that still script their way into our stories...for now, but not forever.
What is their potential for evil; what is their potential for wickedness? That's the only time that those characters become interesting to watch.
When you have to play a character that seems to be a relatively decent person and seems to be like yourself, I think the trick in that kind of character, so that you don't become a cliche, is to find where their weaknesses are.
Oftentimes what happens is that the writer understands one character, but they don't understand the other one, and the other one ends up not being written as well.