What's the most cold-hearted, but real story of cheating you've ever heard of?

I once heard this girl call a radio talk show. On it she admits that she was at a party where everyone was drinking. Her boyfriend got so drunk he passed out.

You’re probably thinking, “Oh, he passed out and she slept with some other guy.” Well yes that did happen and I guess that’s not all that uncommon, but what makes her story perhaps unique and definitely cold-hearted is when she had sex with the other guy, they had sex ON TOP of the boyfriend!

Now that’s some hardcore hatred!