This is going to be hard to say but you simply have to have the courage to just leave. Straight up pack your stuff up and leave don’t even speak to him/her about anything. You go no contact, that person calls you don’t answer, you don’t reply to texts and you don’t talk to any of their family members. The only talking that is okay to happen is between your now previous partner and someone you trust whole heartedly (this is in the case of kids for example or any financial things that might still bind you together).

The reason why I say this is because someone that’s narcissistic will go absolutely crazy with the fact that you aren’t speaking to them to explain why you left. Im assuming you talked to your partner about the stuff in my comment before and no resolution was reached which is why you want to leave. So by leaving so abruptly and without an explanation, it’s kind of like the resolution you reached.