How about I expose my ex-girlfriend?
What is there to expose of her?
She cheated on me and she showed no remorse.
That's so unfortunate you had to go through that. She definitely doesn't deserve you, but I think such things should just be kept secret unless someone asks or gets together with her. Dirty laundry shouldn't be aired out in the open.
I know, right?
Yes, it is never possible to justify cheating on someone for the most part. It is actually good that you warn other people about this person as they could possibly harm them as well. This being said, understand that it is possible for people to change down the line.