I had homicidal thoughts towards my ex
What gave you homicidal thoughts about your ex?
I had them when she was cheating on me with her boss.
Cheating shatters trust and the ability to trust, and people who can't forgive cheating carry resentment. Rather than resorting to violence, communicate with your partner or remove yourself from the toxic situation.
I'll pick the second option since I am not hurting anyone
Good, I'm glad you realize that it's better to just stay away from someone like that instead of considering violence. It's healthier for everyone.