The largest player count FPSes I can think of are Battlefield and Fortnite. I don't think the bandwidth is the constraint on those, even if you really wanted to have 1000 people shooting at each other in the same spot.

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gafferongames 7 hours ago | parent [-]

The number of players per-Fortnite server is 100 players.

The number of players per-Battlefield server is 64 players.

	▲	gafferongames 5 hours ago \| parent [-]
		Furthermore, Fortnite "Cannot support more than 100 players" according to Tim Sweeney. https://www.gamespot.com/articles/fortnite-cannot-support-mo...