The closest matches on Steam are Warfork, Unreal Tournament 3 Black, Unreal Tournament 2004: Editor's Choice Edition, Unreal Tournament: Game of the Year Edition and Robot Roller-Derby Disco Dodgeball.
From the Steam games with at least 2,000 reviews and 80% or more positive, we keep the ones whose main player tags match Splitgate: Arena Warfare's most closely, then show the closest first.
