It's not always in the air. Depending on a hero. Widowmaker it's getting an airshot or 4+ headshots. Junkrat is killing ~3 people with direct hits. Hanzo is just luck, I mean hitting successful shots that you meant to hit 100%. (The same as widow.) Pharah is getting airshots/direct hits and rein is getting a firestrike airshot. And if I'm wrong it's just getting direct hits with proj weapons.