In comics, it seems abundantly clear who are the good guys and the bad guys. If you dress as a goblin and hurl pumpkin bombs at civilians, you obviously see yourself as the villain, right?
But that's not always the case. Some terrorists, mad scientists, or dictators genuinely think they are in the right. Lex Luthor has always stood by the claim that he is the world's greatest hero. Thanos insists that his most diabolical actions were performed, not out of malice, but for his love of death.
But eventually, people like this might have a reality-check and realise that they were a monster all along.
Of course, it can happen to superheroes too. Crimefighters like Captain America or Iron Man are supposed to be uncompromisable, noble, and pure. But heroes are only human (usually) and so, can make mistakes. They might make a bad call, lose sight of why they became a hero in the first place, or become so consumed with anger, they go down a dark path.
Whether they are a superhero or a supervillain, it's heartbreaking to witness a person acknowledge that they are the bad guy.
10. Bane - Secret Six #32 (2011)
In-between battles with Batman, Bane has found time to be an international crime lord, a smuggler, an assassin, a mercenary, a government agent, and a dictator. Considering he's dedicated the majority of his life to villainy, you'd assume Bane has accepted the fact he's a criminal.
On the contrary, Bane absolutely believes he's a good guy! Bane never perceived himself as anything but conscientious and virtuous until he and his team, the Secret Six, ventured to Hell (as you do). As they were leaving, the group were horrified to learn each of them were destined for Hell when they died.
Although certain members like Deadshot weren't too surprised (I mean, he did try and kill the pope), Bane was genuinely baffled that the life he led would warrant an eternity in damnation.
After learning of his doomed fate, all he could say was "But I am a righteous man" over and over while his teammates tried to comfort him. Considering he's broken Batman's spine and killed people since he was eight years old, it's hard to believe it took Bane so long to realise he wasn't a good person.