I found out a few relationships ago that I was "Wednesday girl" so I dumped him on the phone and over a week let ALL of the girls he was seeing know, and ALL of the other 6 SIX dumped him.
five years later, I still inform any girl I see him with, I still spit at him in the streets, and I still inform every employer about his drink problem, because NOT ONLY was he a cheat, I later found out he was a racist as well!!
My short term plan began as hurt him badly, my long term is to hound him to suicide.
When it comes to the girl who cheated on me, I slapped her as hard as I could once, told her I wasn't interested if that's what she wanted to do and left it at that, we became friends, but deep down I would take her back any day she asked. Even 6 years later.
I can appreciate why people cheat, shit happens and sometimes people fuck up hardcore, but when there's another problem I will use it as my cover excuse for being incredibly nasty.