Forgiving an abusive parent is an emotional and personal decision. In fact, it may be one of the most difficult decisions for a child depending on the extent of abusiveness undergone by him/her. But, if you don't forgive your parent, it will affect your emotional well-being in the long run. This is why it is important that you decide to forgive the parent. Here are some important tips in this regard.
1/ The first step is to accept your parent's weakness. You need to realize that at some point or another your parent too, was abused in his/her life. Hence, it must have been a normal occurrence in his/her life. Some parents treat their kids based on their childhood memories. If your parent was abused as a child, he/she may inflict the same pain on you.
2/ Most parents abuse their children when they are under some sort of emotional turmoil themselves. Try to recall the pleasant memories where your parents treated you well. Each time your mind bring back memories of the abusive parent, try to swish it with the pleasant memories you had with him/her. Doing this for some time will help you begin to forgive your parent slowly.
3/ Release the hurt from your mind. Sit quietly and try to recall the moments where you were ill treated by the parent. Feel all the emotions that come up willingly. Feeling an emotion willingly and fully will help release it quickly.