Workspace.Dummy.Controller.Attack:17: attempt to index nil with 'WalkSpeed' ?

local attackCooldown = 1 local attackWindup = 0.5 local attackRange = 3 local attackDamage = 20

local char = script.Parent.Parent local hum = char:WaitForChild("Humanoid") local originalWalkSpeed = hum.WalkSpeed

local canAttack = true

script.Parent.AttackRemote.Event:Connect(function(plrRoot)

if not canAttack then return end
canAttack = false

hun.WalkSpeed = 0.1

local anim = Instance.new("Animation")
anim.AnimationId = "rbxassetid://7209529782"
local playAnim = hum:LoadAnimation(anim)
playAnim:Play()

wait(attackWindup)
local newDistance = (char.HumanoidRootPart.Position - -plrRoot.Position).magnitude
if newDistance <= attackRange + 5 then 
	
	if plrRoot.parent.Player.isBlocking.Value == true then
		attackDamage *= 0.5
	end
	plrRoot.Parent.Humanoid:takeDamage(attackDamage)

wait(attackCooldown)
hum.WalkSpeen = orininalWalkSpeed
canAttack = true

end
end)

Problem:

You are trying to set a value of a misspelled variable, and failed to capitalize the 'S' in hum.WalkSpeed.

Solution:

Fix the misspelled words and capitalization.

Code:

local attackCooldown = 1 
local attackWindup = 0.5 
local attackRange = 3 
local attackDamage = 20

local char = script.Parent.Parent 
local hum = char:WaitForChild("Humanoid") -- the variable you defined
local originalWalkSpeed = hum.WalkSpeed

local canAttack = true

script.Parent.AttackRemote.Event:Connect(function(plrRoot)
	if not canAttack then return end
		canAttack = false
		
		hum.WalkSpeed = 0.1 -- this was "hun.Walkspeed"
		
		local anim = Instance.new("Animation")
		anim.AnimationId = "rbxassetid://7209529782"
		local playAnim = hum:LoadAnimation(anim)
		playAnim:Play()
		
		wait(attackWindup)
		local newDistance = (char.HumanoidRootPart.Position -  plrRoot.Position).magnitude
		if newDistance <= attackRange + 5 then 
		
		    if plrRoot.parent.Player.isBlocking.Value == true then
		        attackDamage *= 0.5
		    end
		    plrRoot.Parent.Humanoid:takeDamage(attackDamage)
		
		wait(attackCooldown)
		hum.WalkSpeed = orininalWalkSpeed -- this was "hum.Walkspeed"
		canAttack = true
	
	end
end)