The fic was definitely on AO3, but it vanished and I cant find it! It was post-war, Harry was still the boy-who-lived, but Draco had never gone to Hogwarts. There was a serial killer going around and killing men (rich, young and handsome, i think?) the 'muggle way' - not using magic - just strangling them or something. Harry was this serial killer, and I remember him having a conversation with Hermione and Ron about it in the 1st chapter, talking about how they wish the killer gets caught fast, etc etc.

And one night, in a restaurant/bar, harry sees draco and thinks that he's the perfect next victim - so he talks to him. And later, Harry stalks Draco and breaks into his house because he likes to 'know his victims personally' before killing them (?). And when he enters Draco's house at night to kill him, he ends up sleeping with Draco instead (like serious dubcon) and Draco had really enjoyed being dominated like that and gets into a relationship with Harry, and Harry felt like he didn't need to murder in order to 'scratch-the-itch' and finds that sleeping with Draco satisfies him the same way.

I remember Harry being really possessive/dominant. And eventually he decides to kill again, and draco, thinking that Harry is cheating on him, follows Harry and finds out that Harry is the muggle-serial-killer. But Draco ends up not leaving Harry because he's pregnant?

I remember it being strictly bottom!draco. And it was a completed story with a WIP!sequel (that was updated this year - but I can't find that either!)