Aristotle

Aristotle was a Greek philosopher. In his poetics he had a set of rules that described an ideal narrative. One of them was that every character has a flaw. I think this has widely influenced film. Aristotle's poetics

In 'Spider Man 3' Peter Parker who is spider man gets possessed by a symbiote and his spider suit turns black. This brings out a more vengeful side to him and even when he's not wearing the suit he changes his hair and clothes and thinks he's better then everyone else. When before this he was the kind and sensitive hero and planning to propose to Mary Jane, but then he goes out to make her jealous. Spiderman

Another example of a character having a flaw is Harvey Dent in 'Batman'. He's the DA and plans to get rid of the mob. But then he and his fiance get kidnapped and she gets killed. Also half of his face gets burned off and he becomes the baddie 'two-faced'. Dent then goes out killing people to get revenge for his fiances death. Batman also becomes flawed in the eyes of the people of gotham. He tells the police to blame him for the deaths because he doesn't want them to lose faith.
two-faced