How to beat a hacked overpowerd pokemon?

My friend has a hacked rayquaza and mewtwo. He beats me all of the time but the only reason i lose is because i kill his other pokemon then i get weaked by his overpowered mewtwo and then his overpowerd rayquaza finishes me off. He calls this stratigy. I dont know what to do. I try using moves like double team but his pokemon are too good. We both have all level 100s but his are hacked. Also he says if i use mewtwo or rayquaza he will battle me again. How do i kick his a## or should i do it in real life?