You can't. Walk away as a narcissist has more ammo than you will ever have. They can turn any situation around and all of a sudden you are the bad guy. They won't rest till the world sees their point of view.
That's not the definition of a narcissist at all.
It may not be your definition but it sure is mine and narcissim has a broad range of definition.
Don't give them your attention, and don't congratulate or emphasize on their successes because this just validates you are inferior and they are better (in their eyes). I had a friend who called himself a best friend, but acted like he was superior to me; arrogance, belittling and undermining. It was one of the worst experiences too, after I had returned to a city and moved in with him because the last place I lived was a disaster; not meeting quality people for friendships, to only encounter this arrogant snob! I grew to seriously hate him. They really hate it when they are talking and you act as if you are pre-occupied with something else, or when they are bragging about something and expect for you to praise them but you don't or you don't act like you heard them, ha ha !
Try it but do be careful, they really don't handle rejection well.
They are not the type of people you really want to provoke, I say walk away and count your blessings you are still standing.
My husband is one (not with him now) and a female friend was one as well. Horrible terrible people, I don't play mind games and really wonder how they get the energy, but it is bread and butter to them. If you can just slip out of their lives quietly. Let them think it was them, any rejection from them run with it. How I escaped.
Oh I hear you, my mum has issues as well. What can you do? I limit my time with her everyday would kill me.
Sorry, my relationship with my mum improved once I moved out. Remember the best revenge is living well. Hope you can move out soon.
Smear ugly-dust on his mirrors. It's on the shelf next to the fairy-dust.
stop paying attention
Shave his eyebrows off when he's asleep.