Some people are just born evil. Or they're born with something broken in their brains that can never be fixed.
Go talk to some teachers. Ask them about the worst of the worst. You'll hear some stories.
You hear a lot about "the school to prison pipeline," but there are some kids that you can just look at them and say, "that kid is going to die in prison." I'm talking about kids that assault their teachers and other students. I'm talking kids that steal, lie, and manipulate people in cruel and vindictive ways. In some cases they make a game out of deliberately creating false allegations of inappropriate behavior on the part of their teachers. They actively seek to destroy lives. I'm talking about kids that go through every program and intervention, that receive every form of support and counseling imaginable. Kids that receive nothing but compassion, caring and understanding...and respond by treating other human beings as disposable garbage fit only for their amusement. It's a rare kid that is truly this evil, but there are some real monsters out there. Some people are just born evil. There are some people that will simply never see the humanity in other human beings. There is no amount of counseling or coaching that can fix such profoundly broken souls. The best we can do is to warehouse them, to lock them in a place with their own kind, where they'll never be able to hurt an innocent person ever again.
You cannot teach someone to have empathy. You cannot teach someone to care for other people. You either do, or you don't.