Who's a bad guy/villain you genuinely understood?

Not rooted for. Not thought was cool. Understood. The kind of character where you watch their story and think "I don't agree with what they did but I get how they got there." The writing was so good you couldn't just dismiss them as the bad guy.

For me it's Clyde Shelton in Law Abiding Citizen. The system failed him in the worst possible way and his rage made complete sense even when his actions didn't. Who's yours?