Mewtwo is. No doubt. Do you know why. Ok.
Let's begin with the first pokemon movie. Mewtwo makes his own pokemon, mewtwo is the strongest psychic type or was suppose to be. He can also take the minds of entire cities, like he did in the movie. He killed Ash. Ash, the main character. The only reason why he came back is because he let the pokemon cry and he felt bad for the idiot. If anything Mewtwo could of destroyed the pokemon himself. Also, the fact that he is intelligent and can speak the human language. Besides mewtwo, he can **** with people's heads. He was also powered up with that power suit giovanni gave to him. So think about it, he has his own castle, he stole the minds of the town near him, he MADE his own SUPED up pokemon what makes you think that he won't make a clone of a stronger pokemon and have them kill each other. Mewtwo could really take out the pokemon himself, but he knows that its a waste of time for him. That's why he goes after mew because he wanted to know who was stronger. We also knew that Mew barely stood a chance against mewtwo, and mewtwo would of won if it wasn't for stupid ash.