Are you saying it is a correct thing to do? There are two options. A correct thing and an incorrect thing. Abusing a child - hitting them in any way - is always an incorrect thing. That is what the word mistake means. It is the wrong choice.
"It is to the parents to take care of their kids and not anyone else!"
That is also not true at all. All it takes to make a child is to have sex. By your logic, if a man raped a teenage 11-year-old-girl the man is a parent and gets to take care of that child. Many times it is up to others to take care of the child and NOT the parents. Many parents are just not meant to be parents. Having sex is just a physical act. Caring for a child requires far more talent than that.
It is never easy to forgive. But it is important for YOUR HEALTH that you learn to. It's not like you're hurting them with your stress. You are only hurting YOU. You are hurting yourself every day, just as if you are stabbing yourself with a knife.
You need to stop hurting yourself. Either you need to move away or you need to learn to release the stress. It makes zero sense to actively try to hurt yourself more, when every day is precious.