The True Meaning Of Broken~ Nightmare Sans x Reader

you know pretty much all the sans in the multiverse and you get along with mostly all of them you were also a very close friend to a certain blue little cinnamon bun underswap sans but you called him blue for short.
you and cross were pretty much siblings and you could also see chara which gave her another person to talk to not to mention that you were also friends with him and his group even though the leader 'nightmare' was the king of nightmares he was nice to you and the others because he thought of you guys as his responsibility so he would take care of you all
nightmare let you visit blue because he knew that he wasn't a threat and he was only one of the people to be able to help you keep your 'insane side' under control
only blue and cross were able to control your insane side and lets just say that without it well...
things get real messy
usually you were really nice dispite your love to destroy things and if someone were to hurt someone you cared about well they died so yeah death was normal for you guys did i also mention that you were a destroyer of au's too
your job when nightmare went out destroying au's was to cover his blind spot since he only has one eye you cover the spot where he couldn't see just to protect him
okay you have a small crush on nightmare but oh well its not like he's gonna love someone as broken as you
what happens when one day your going to visit blue in underswap only to find his dust surrounded by golden dust and paint?
lets just say...

SOMEONE IS GOING TO HAVE A VERY BAD TIME