Search sociopath , narcissist. There is something absolutely a wound unto itself when one derives pleasure from another's pain. Betrayal trauma is something to research as well.
Yes I have had relationships with narcissists and sociopaths. They know exactly what they are doing and want to ruin/destroy others. I have seriously cried or was upset in front of them and you see a smirk and ure joy radiating out of their eyes. I'm sorry but I don't think of them as humans. Pure evil. No humanity in them, and they hate those who have it.