I have a few so I'll go one at a time and I'll start with the obvious--Lucius Malfoy.

These probably aren't the best qualities to like in a person but he's unforgiveably evil. He doesn't make excuses for it and he's extremely manipulative. He can get anything he wants, at any time because he has such a way with words (and money). He does many things just for public's sake but he is no doubt devoted to the Dark Lord. Lucius in the presence of Voldemort is the only time we actually see him scared. Just to see that one weakness, it's nice to know he's this flawed character (severely). And it doesn't help he's portrayed by Jason Isaacs whom I love and so he's been the only Lucius I've known. I saw the first three movies before I read the books so the characters up to Azkaban were already determined for me.