"Deal breaker!", "Final Straw!", "We're Done!" or "You're dead to me!"
Forgiveness means you will no longer allow something to dwell on your mind anymore. In a sense forgiveness is a gift you give yourself.
However it doesn't mean one has to continue to associate with a person. The true opposite of love is not hate. It's "indifference".
"Anger is the Mask that Hurt wears!"
If you're angry it means you're still "emotionally invested".
When someone "no longer exists" in your mind or you view them like any other "stranger" with no known history and devoid of passion it cuts deep. However you can't get there until you let it go.