I seems you have done the best thing, which is remove their negative energy from your life until they make a sincere apology. But I would imagine your expectation goes beyond the apology. It would also include their improved behavior after the apology. That is something I have had to learn as part of my journey focusing on trust. It is not just enough to apologize and be sincere, you have to show it through actions and follow through.
As a psychopath, he has a massive ego, and feels above apologizing to other people. Often, he would do somebody dirty and then try to talk to them normally as if nothing happened.
I did a lot of research on psychopaths, and you likely know that their brains are different from normal people. The area that controls empathy, guilt and compassion, appears to be un-wired or switched off. If I do something wrong or see someone suffering I feel guilt and compassion. If he does the same thing, he feels joy.
He once showed me videos of two girls cutting their wrists because he broke up with them.
He was smiling the entire time...
He would break up with a girl on the phone and then smile in front of me as she cried. He said his condition is genetic and many males in his family have this inborn cruelty. These people are absolutely inhuman, and since there's no cure for this, I think they should round all of these people up and send them to "Psychopath Island" where they can live out their days hurting each other and leave the rest of us alone.
oh wow! not much can be done there I don't think. Sounds like a lost cause possibly. Best avoided for sure.