Would it bother you if your significant other was friends with your worst enemy?
If it was a friendship that has been there for a long time, I can live with it. But, I know if I asked her to drop him/her as a friend, she would. I would do the same.
My significant other is my best friend. If I disliked someone that bad it would be for a good reason, and he would have my back.
Yes. It would ruin our relationship.