I'm going to ruin my ex's marriage
Why do you want to ruin their marriage? Aren't you broken up?
She deserved it for putting me through hell
I get that it hurts when a relationship ends. You should not go out of your way to ruin a marriage over it though.
There is more to it than you think.
Regardless, you broke up and need to move on, just like they have. You don't want to waste any more time on a relationship that hurt you. Find someone else to fall in love and forget the past.