Yeah it happens everyday…unhealed children who are also molested have potential to become an abuser when they are adults

People who are suffering from PTSD can be very difficult to be around and some of their actions could be deemed as abusive, although I think in that case, it would be unintentional and a trauma response which they would need therapy and treatment for.
I think it's more likely that children who were raised in an abusive family situation could grow to become abusers if they never know loving ways of communication and don't develop secure attachments with people who can show them appropriate and loving ways to communicate feelings although even that's not a given. 😊

If they train hard enough

It happens, especially in the case of abusive parents. The child grows up believing that this is what parental love looks like, and then they do the same when they become parents.

I know a guy who is in prison, partly for this reason.

I think so. Especially if it was during childhood. That's where we learn how to be in a relationship. We are all products of our environment.

Thats what the psychologists were warning me about with my ex. That she might abuse our son. The actually suggested that we get a divorce. Two of them did. Eventually she left and i was a single dad.

Yes.
Not always but it´s not so rare.

Yes, it's called 'reactive abuse'.

practice makes perfect..

Absolutely. Many abusers were once abused themselves

Yep

Yup. People can become the very thing they hate

Happens with families where someone gets abused by their parents, but then grows up to be the same shitty parent that they hated