If you've been victim to a bad situation and you've left, but you still keep bringing it up in your mind, thinking of why they should be punished. You are holding onto anger within yourself and putting yourself through more grief. Not only does this bring you out of living in the moment which is where you will find peace of mind. Your energy you are sending to them will keep the other person locked in defending himself, which will prevent him looking at his or her truth.
Once you let go of trying to teach them a lesson you cannot deliver because your relationship has ended, you will realize that you're free to now explore creating something new with your mind, as your projected energy will release their defending themselves to either create what they want or if in the case of a Narcissistic nature, they will move onto the same patterns until they start to see the truth of their patterns.
And in these intense energies that will happen directly.
So empower yourself and LET IT GO! you will be doing not only yourself justice but will also release them to see themselves fully.