Get over it and move on.
I had a boss that I really had a horrible experience with - was a huge jerk and more. Some years later karma visited him and he was knocked down a couple of notches. Some business associates say that he is now a changed man and I have to admit that I am a little bit happy that he got himself squared away.
Id travel back in time and become a valuable member of the work force. Thatd show him
I've had a couple real turd sandwiches for bosses. You really want to get their collective goat = move on and be successful. Leave them behind to stew in their own ineptitude.
I've also had to fire a couple of people. And if I had to do it all over again, I'd do it again, no questions asked. I'm pretty sure that to this day they don't really understand why they had to go. It really wouldn't matter how many times it was explained to them, they just don't get it. - Don't be the guy that thinks the world revolves around him and can't see their effect on others.
So move on, do well and let karma do it's thing to the turd, and try not to ever become a turd yourself.
Well I was let go because the manager rehired someone (his minion friend) who left the company for more money in another state and came back when he couldn't sell his house.