"If a human simply does not draw a bad certain from his actions? Harms other people and feels no compassion?" -
Taking morality out of the equation, there are people that enjoy harming other species or other humans... that is the main definition of being bad, just harming for the sake of it, and it doesn't has to do anything with environment or education.
"But which misconduct can no longer be forgiven and make a person a bad person?"
There are also different kinds of "badness" some may be due to psychological disorders, but still even if it isn't their fault when the conduct repeats itself and starts producing "pleasure" or a satisfying effect on the perpetuator... I believe that is the thin line that separates a mistake or a misconduct form someone that is "bad".
People who feel no compassion or who have empathy deficit disorder are flawed but not bad. Every human is flawed even if not in the same way. If we all strive to be better then we can try to transcend our flaws and this is the best I think anyone can hope for.
Compassion for a certain extent can be taught. Empathy on the other hand is something the brain just does and is not taught. If we see someone do something compassionate we should reward that or at least acknowledge that they did something amazing as a society.
@seb.vicke i think you describe sociopaths. They can feign feelings and empathize but prefer to be unfeeling. sociopaths also usually have a sadistic streak, some can deal with it and live it out in their own way and others are subject to it. But that should not mean that all sociopaths are bad. And as far as I know sociopaths were not born that way but something in their childhood made them what they are.