How to make a script that kills the player on join?

I tried to make a script that kills the player when he joined (because there's a spawn bug) but I don't know how. Can you please help me?

First your going to want to use a PlayerAdded event

game.Players.PlayerAdded:connect(function(player)
--Code Goes here
end)

Then your going to want to kill the player, the way you can do this is by waiting for the characater then getting the humanoid and setting the health to zero and removing the forcefield.

game.Players.PlayerAdded:connect(function(player) --Waits for player
	player.CharacterAdded:connect(function(char) --Waits for character
		wait() --Waits so they can kill
		char:WaitForChild("ForceField"):Destroy() --Destroys ForceField
		char:WaitForChild("Humanoid").Health=0 --Sets Health to zero
	end)
end)

That should work

I suggest this being a Server Script:

game:GetService("Players").PlayerAdded:Connect(function(plr)
	local character = plr.CharacterAdded:Wait()
	character:WaitForChild("ForceField"):Destroy()
	character:WaitForChild("Humanoid").Health = 0
end)

Hope this works!