How to find who killed a player?

The thing is, no one actually "kills" someone. I don't have that much time so here is a quick summary: The way of counting kills is by "tagging" the player, within whatever script you use for your attack. Examples can be shown on the "linked sword". When a player dies due to this attack, the player that fired the attack is tagged, and that is put into further code into making a "Ko" system. It's easy with gears, could get tricky with other attacks. I'd love to help you out more, but your question seems more of a request. You have no script whatsoever, and want a Ko system handed to you, without even stating details.

I found this in models on ROBLOX, I hope this helps. Made by: Demonzombietoy

function onPlayerEntered(newPlayer)

    while true do
        if newPlayer.Character ~= nil then break end
        wait(5)
    end

    local humanoid = newPlayer.Character.Humanoid

    humanoid.Died:connect(function() onHumanoidDied(humanoid, newPlayer) end )

    newPlayer.Changed:connect(function(property) onPlayerRespawn(property, newPlayer) end )


end

function Send_DB_Event_Died(victim, killer)

    local killername = "unknown"
    if killer ~= nil then killername = killer.Name end
    print(victim.Name, " was killed by ", killername)

    if shared["deaths"] ~= nil then 
        shared["deaths"](victim, killer)
        print("Death event sent.")
    end
end

function Send_DB_Event_Kill(killer, victim)
    print(killer.Name, " killed ", victim.Name)
    if shared["kills"] ~= nil then 
        shared["kills"](killer, victim)
        print("Kill event sent.")
    end
end



function onHumanoidDied(humanoid, player)
    local stats = player:findFirstChild("leaderstats")
    if stats ~= nil then
        local deaths = stats:findFirstChild("Wipeouts")
        deaths.Value = deaths.Value + 0


        local killer = getKillerOfHumanoidIfStillInGame(humanoid)


        Send_DB_Event_Died(player, killer)
        handleKillCount(humanoid, player)
    end
end

function onPlayerRespawn(property, player)


    if property == "Character" and player.Character ~= nil then
        local humanoid = player.Character.Humanoid
            local p = player
            local h = humanoid
            humanoid.Died:connect(function() onHumanoidDied(h, p) end )
    end
end

function getKillerOfHumanoidIfStillInGame(humanoid)

    local tag = humanoid:findFirstChild("creator")


    if tag ~= nil then

        local killer = tag.Value
        if killer.Parent ~= nil then
            return killer
        end
    end

    return nil
end

function handleKillCount(humanoid, player)
    local killer = getKillerOfHumanoidIfStillInGame(humanoid)
    if killer ~= nil then
        local stats = killer:findFirstChild("leaderstats")
        if stats ~= nil then
            local kills = stats:findFirstChild("KOs")
            if killer ~= player then
                kills.Value = kills.Value + 0

            else
                kills.Value = kills.Value - 0

            end
            Send_DB_Event_Kill(killer, player)
        end
    end
end

game.Players.ChildAdded:connect(onPlayerEntered)