Relationship with bad parents (kamma and issues) One of the main sources of bad kamma in Buddhism is doing wrong to your parents and not taking care of them. Buddha said it is very very hard to repay your parents, however how should one behave if he or she has bad parents? Maybe a parent that was an alcoholic or didn't take care of him properly, abandoned him, banned from his house or maybe stole from him? There are countless possibilities, what to do?
My father was an alcoholic, and I suffered a lot of grief from him - so I might as well try and answer this one.

The way my first teacher taught me about this (back when my father was still alive and I still encountered him a lot) the circumstances like this come from our karma, specifically from our attachment to decency and spirituality. The more we are attached to decency and to spirituality, the more we hate people who are indecent and lowly, the more we will have to face them. So the only way to stop this particular kind of painful circumstances, is to drop the attachment to decency and to spirituality, by no longer putting decency and spirituality above love and above existence itself. This was the teaching method my first teacher employed, very effective.

The way my last teacher taught me about this, long after my father passed away, is that in such cases freedom comes from forgiveness, understanding, the intent to stop the chain of suffering. We should understand that family issues are passed down the chain, although not necessarily in the same form. When father has certain issues, the child will have certain other issues - that will affect lives of their children and so on. Even my father's behavior was not his own, he inherited it from his childhood family - his father was a very violent guy, a commander of a penal military unit, a place where the criminal soldiers served. Behind a violent alcoholic there is often a hurt little boy. This is important to understand.

So these are two lessons from my Buddhism teachers, one is to let go of attachment to decency and spirituality and abandon hatred and aversion based on them, and two is to understand your parent's own background and suffering.

As to what to do, I think the best way to work with such people is as if you were working with a child. No matter how adult they look or pretend to be, if they act like that they are still immature, far from it. So working with them like you would with your own child, with tough love, compassionate but strict, seems to be the best course of action.