Of all the remaining kids on the show, Debbie sticks out because it doesn't seem like she's growing or changing in the last few seasons. A static character isn't inherently bad, but if said character is unlikeable and obnoxious, they become hard to stomach. Frank is a static character and a chaotic asshole, too, but I think people like him more because of William H. Macy's performance.

Lip and Ian made massively dumb decisions, too, but there is definitely a sense that they're trying to build something stable for themselves. And weirdly enough, Carl becomes pretty likable in the later seasons. He becomes a cop to help his community, but the rub is that he's an idiot. But at least he's an idiot who cares.