I'm going to destroy my cheating exes' relationship
Why do you want to be so spiteful?
Because I want her to know that I'm more mature than him
That is the wrong way to show that! Intentionally destroying a relationship to hurt people is not the way to show that you are mature.
They will know next year that I'm the better person.
If you want to be a better person, you need to do good things. Hurting your ex intentionally is bad and will not make you look good.