How do you make a one vs everyone game?

OK first of all I need to clarify that this doesn't have to do anything with scripting.Second you need to go into roblox studio choose the place you want teams in go to advanced objects click teams and enter your team names since you want two teams.Glad that helped and make sure to change the current name of your team.

You question is generally a broad topic, but if you want the mechanics on how you want to select a random person to be the 'beast' and everyone else as 'human' then you would need to get players and then create the game setup. It's pretty straightforward if you know how to script.

local p = game.Players:GetPlayers()
local plrSelected = math.Random(1,#p)

for i = 1, #p do if (p[i] == plrSelected) then
-- Other stuff goes in here to setup your 'beast'
else -- They are 'human'
-- Other stuff goes in here to setup your 'human' (give weapons, health, guis, etc)
end

add to your place battle tools. or you can create a new place and set the template as strategy or action