In Another Life (слэш)

Katsuki's never been one for gentle words, but from the wild panic in Deku's face, he knows this is the time for it.
"Deku—" The weapon presses a little harder against Katsuki's forehead and he stops, getting his bearings. "Fine. Midoriya, then. Look. I'm not going to hurt you. I swear. I'm just looking for some answers I'm hoping you can provide."
After a battle gone awry leaves Katsuki stranded, he seeks out one of the few people he really trusts: Deku. Except when he finds his hero partner, he looks completely different, and the first thing he does is put a gun to Katsuki's forehead. So that's different.
Canon-divergent future fic where Katsuki gets sent to a parallel universe during a villain battle. One where Izuku's a cop instead of a pro hero, and Katsuki himself has been dead since middle school. In a world that's different enough to be strange and similar enough to be familiar, Katsuki does whatever it takes to find his way home.