"Write me the most complex sword script you can make"

I'm not sure about the "most complex" sword script, but here's a sword script with multiple features such as damage, knockback, and a special ability that can be activated with a cooldown.

```lua
-- Server Script
local Sword = script.Parent
local Handle = Sword.Handle
local Damage = 25
local KnockbackForce = 10
local SpecialAbilityCooldown = 5
local SpecialAbilityActive = false

local function onTouched(hit)
    local character = hit.Parent
    local humanoid = character:FindFirstChild("Humanoid")
    local swordWielder = Sword.Parent.Parent

if humanoid and swordWielder ~= character then
        humanoid:TakeDamage(Damage)
        local knockbackDirection = (character.HumanoidRootPart.Position - swordWielder.HumanoidRootPart.Position).Unit
        character.HumanoidRootPart:SetNetworkOwner(nil)
        character.HumanoidRootPart.Velocity = knockbackDirection * KnockbackForce
    end
end

Handle.Touched:Connect(onTouched)

-- Local Script (inside the sword)
local Sword = script.Parent
local UserInputService = game:GetService("UserInputService")
local Cooldown = false

local function activateSpecialAbility()
    if not Cooldown then
        Cooldown = true
        Sword.SpecialAbilityEvent:FireServer()
        wait(Sword.SpecialAbilityCooldown.Value)
        Cooldown = false
    end
end

UserInputService.InputBegan:Connect(function(input, gameProcessedEvent)
    if input.KeyCode == Enum.KeyCode.E and not gameProcessedEvent then
        activateSpecialAbility()
    end
end)

-- Server Script (inside the sword)
local Sword = script.Parent
local SpecialAbilityDamage = 50
local SpecialAbilityKnockbackForce = 25

local function onSpecialAbilityActivated()
    local character = Sword.Parent
    local humanoid = character:FindFirstChild("Humanoid")
    local target = Sword.Target.Value

if target and humanoid then
        target.Humanoid:TakeDamage(SpecialAbilityDamage)
        local knockbackDirection = (target.HumanoidRootPart.Position - character.HumanoidRootPart.Position).Unit
        target.HumanoidRootPart:SetNetworkOwner(nil)
        target.HumanoidRootPart.Velocity = knockbackDirection * SpecialAbilityKnockbackForce
    end
end

Sword.SpecialAbilityEvent.OnServerEvent:Connect(onSpecialAbilityActivated)
```

This script creates a sword that deals damage and applies knockback force to the character it hits. Additionally, it has a special ability that can be activated with the "E" key, dealing increased damage and knockback force with a cooldown between uses.