To be defined as a bad guy usually requires that you consistently do bad or that you do such a level of bad that your reputation cannot be redeemed. If you commit cold blooded murder without any reasonable justification there is no coming back from that. You're a bad guy. If your worst crime was to steal a car in your youth, but you then go on to lead a model life, you could not reasonably be described as a bad guy. Perhaps at the time but not as an everlasting label.
