"You" inspired question

Watching the show You and it made me wonder what I would do if I were with my partner for a long time. Say 50 years, we are old and loved each other deeply the entire time, he is the one. Then I find out that he did some Joe shit, let say stalked me and manipulated me into being with him and killed an ex, how would I feel and what would I do. I can't say for certain I would leave, I would be shocked and horrified but would that outweigh the long life I spent with him...happy? I dont know.

What would you do? Would you leave him or would you forgive him and cherish the time you had despite the things he did?