Death wall that kills you is to laggy? Help.

I can imagine this lagging if:

• You have this script copied in tens or hundreds of parts
• The wall parts are very large

You say these parts are moving using TweenService. If the walls are also large, I'm not surprised it's lagging! You are likely asking Roblox to essentially scan a huge area and report to you every part that it can find every frame (since TweenService runs constantly).

To fix this, you need a different approach - every frame, use math to check whether a player is "in bounds" or else in contact with the death wall. If they're out of bounds (but still in the map area -- ex, not in a lobby), then set their health to 0.

You probably need to use a debounce.

If you don't know what a debounce is here's a basic explanation:

local debounce = true

function touched()
    if debounce == true then
        debounce = false
        print("I have been touched!")
        wait() -- How many seconds until it can be touched again
        debounce = true 
    end
end

script.Parent.Touched:connect(touched)

So if you wanted to apply this to your script then you would write something like this:

local debounce = true

function KillPlayer(part)
    if debounce == true then
        debounce = false
        h = part.Parent:findFirstChild("Humanoid")
        if h ~= nil then
            h.Health = 0
        end
        wait()
        debounce = true
    end
end

script.Parent.Touched:connect(KillPlayer)

I hoped this helped you!