How Do I Make A 'Death From Certain Height' Script?

I've tried using altitude, Enum.HumanoidStateType, e.t.c. I've given up. I don't know how to make a script that damages a player from a certain height!

Well, just check when the BodyHeightScale changed, and if it's higher than you want, it kills. Something like this:

-- this have to be on a serverscript tho, so do it in the onserverevent where you change height
player.Character.Humanoid.BodyHeightScale.Changed:Connect(function()
	if player.Character.Humanoid.BodyHeightScale.Value >= 2 then -- determine a value here
		player.Character.Humanoid.Health = 0
	end
end)

Something like this, hope i helped.