How about some dark and gritty crossovers:
Souls Art Online 1 - 21.1
A Sword Art Online/ Dark Souls Fanfiction
Summary: A fic in which Kayaba decides to put the player's humanity on test as they try to rekindle the flames, constantly struggling against the Kingseeker system that keep amplifying the difficulty.
....F**king Tinkers 1 - 4.6
A Sword Art Online/ Worm Fanfiction
Summary: A fic in which Taylor Herbert ends up trapped within the world of Sword Art Online, where the AI slowly begins to override Kayaba's control, and where the death toll rises with the stakes.