Do you know how sometimes you have a bad day, and it may cause you to be a bit short with your kid or partner? And then, later, you go to them and say: I am sorry I was short with you, I was just worried/tired/busy/other, … We all do that, right? Well, not the toxic person. They live in a blissful world where nothing is ever their responsibility. When bad things happen, it is because the world is against them! When they are raging abuse at you, it is because YOU made them angry.
The narc will never stop stepping over your boundaries. For as long as allowed to they will continue to do so with utter contempt for your principles. The only way to stop them is to cut them out of the equation of your life. It can make the narcissist angry. That evil narc is beneath the level of contempt. Void of understanding and empathy. They just don't care who they step on and hurt in the process.