Keybind Za Warudo is spammable. Any help?

Put the wait inside of the if statement for your debounce. The only reason it should wait 20 is for your debounce; the only way it should get to that point is if the debounce is passed. When you put it outside of your if statement, you're forcing the player to repeatedly wait 20 even when they haven't passed the debounce check, since it's outside of that scope.

The reason it isn't waiting is because you're making the debounce false after any key press, not just Q. The player can spam any key to re-fire the event which causes the wait to repeat in on itself, which essentially causes there not to be a wait.

local UIS = game:GetService("UserInputService")
local Event = game:GetService("ReplicatedStorage"):WaitForChild("Events").Abilities.ZaWarudo
local Player = game.Players.LocalPlayer
local Debounce = false

UIS.InputBegan:Connect(function(input)
    if input.KeyCode == Enum.KeyCode.Q then
        if not Debounce then
	        Debounce = true
	        print("Za Warudo triggered by "..Player.Name..".")
	        Event:FireServer(Player)
	        wait(20)
    		Debounce = false
        end
    end
end)