Mine was when an ex-girlfriend of mine slept with my roommate soon after we broke up. Thats obviously not that bad because we were broken up but what made it bad was during that time, she was leading me on saying that we were just taking a break and we'd be back together soon, which was an obvious lie.

I finally snapped when she came to my apartment one night crying, wanting sympathy from me because, come to find out, my roommate had just used her for sex and she was very upset about it. Her expecting me to feel bad for her after how she'd wronged me, I just exploded. I told my friends everything and was in a trance of anger that I hope never to experience again.