Rakion : Chaos Force
With this game you have two ways to play: battle mode and stage mode.In Stage mode you will fight against NPC,you can't fight other palyers,you can Cooperate with other players to fight NPC.In Battle mode ,the player can fight together.There’s Solo Death Match, Team Death Match, Golem War and so more.

The requirement isn't high,you can check it at:
Website: http://rakion.softnyx.net/