For those in a relationship, what is the one worst thing your partner can do, which is over for you?

So in my previous question, I asked whether you would forgive a drunken partner who cheated on you, and two users said it isn't the worst thing that can happen in a relationship. Which was interesting and made me thing of possible general scenarios where it would be the end for me. For me I still think, cheating is the major thing. What is it for you?

With general I mean the normal things that happens to most users here. Not murder or committing a crime.

For those in a relationship, what is the one worst thing your partner can do, which is over for you?
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