Regulus Black and Jason Todd
My fav au (which I did create), is the concept of Regulus Black crawling out of the grave after being killed by Peter (whom has a reason to kill I love u Peter I’m sorry), and wanting revenge only to be disappointed by Sirius (in this au he’s Nightwing/Dick Grayson and is also the one to be “blamed” rather than Fleamont who is retired Batman/Bruce Wayne). Regulus holds Sirius accountable, not understanding that Sirius is already feeling a lot of guilt and shame.
Regulus tries to get Sirius to kill Peter as revenge but because Sirius is at a constant state overcompensating, he refuses due to the guilt he feels for being a part of what drove Peter to insanity. Regulus of course gets frustrated and thereby becoming Noir (this au’s red hood).
From there on a lot goes down I’ll expand on it in the fanfic I’m writing! :3