Gooigi

Gooigi is Luigi's stand and is able to fight on his own without Luigi. He has previously fought Mario and Wario (not at the same time, mind you), but never Waluigi. Gooigi is dangerous only if you are against Luigi... for whatever reason. Gooigi can always be trusted as he sides with the good guys because  Luigi  sides with the good guys. Whenever somebody starts to fight Luigi, Gooigi will typically appear (unless he is busy).