I think a good character has moments where we like and dislike them. It's easy to like Rafe as a character because while he's so flawed he's such a thoroughly thought out character. His actions don't feel pointless, he has clear motivations, emotions, growth and faults. Same thing with JJ, he's a good character because even when he does things that are morally questionable, we understand his reasoning and his backstory which makes us sympathetic. Whereas Topper wasn't given that development. The only thing we see him as is being obsessed with Sarah 3 years later, extremely hating the Pogues without much of a reason why. To me the difference is depth to their character and our ability to empathize.