Place it immediately after the moment of impact in a short edit, with Enemy Spotted just before it to set up the danger, then follow it with Roblox Oof as a second reaction to the same hit.
Über diesen Sound
This under-a-second clip is Scout from Team Fortress 2 letting out a sharp, pained 'augh' after taking a hit. It lands as sudden, comic hurt, the kind of exaggerated yelp that makes a bad moment feel funny instead of serious. The voice is young, brash and instantly recognisable to players of the game.