What is the best way to get revenge please read all?

So I am with someone who means everything to me and his ex is a real piece of work with me and him because he is with someone that is not him (they split up long before we got together) she has not let him see his son for Christmas or ever now it's unfair to him and his son I need help I don't want to play nice the her any more
What is the best way to get revenge please read all?
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