I recently have been working on a spleef game where the last person alive wins. The problem is, I don't know how I would detect the last player alive. I was thinking I could do it with a scoreboard but I don't know how I would do that, and all the tutorials use /testfor which doesn't exist in 1.13. What would be the best way to do it?
P.S. there also might be players joining a lobby area in the same world as the spleef arena while a game is in progress (it's for a server)