Humans like to attribute the representation of certain things to certain Pokémon, such as Rayquaza and the sky, Giratina and antimatter, Xerneas as life and etc. While technically untrue it's all fair and good, but I just want to remind everyone that what should be attributed to Mewtwo specifically is combat. Battling, fighting, violent conflict, whatever you want to call it.

Mewtwo was engineered for the purpose of fighting. Its combat abilities were raised to the ultimate level and it can think of nothing but destroying its enemies. It's an organic fighting machine. Thus in a way it is combat and battling ability that Mewtwo represents.