The philosophy behind Mewtwo’s creation was to make the world’s strongest Pokémon. Since Mewtwo is a clone of Mew, there seemed to be only one Pokémon that could match him at the time of his original creation. However, has vastly expanded its universe since Gen 1 to include more powerful Legendaries, Mythicals, and even Ultra Beasts. Some of these are even deities that can stand toe-to-toe with the lab-created powerhouse. Despite the power of Mewtwo, however, there are other Pokémon who are more powerful.
In the years since Mewtwo's first appearance, the franchise has continued to come out with more games and memorable monsters. For example, the most recent Gen 9 games have introduced Paradox Pokémon and even Stellar-types that are incredibly powerful. These newcomers come equipped with new techniques and battle strategies that make them unique challengers for Mewtwo's reputation as one of the most powerful Pokémon in existence.
Not surprisingly, Arceus is one of the strongest Pokémon in existence. Being the god of all Pokémon (who also created the universe), Arceus has an incredibly impressive power level. Arceus excels in combat by taking advantage of type weaknesses, resistances, and immunities. With the capability to switch his type on the go, Arceus would be able to land the Bug-, Dark-, and Ghost-type attacks that Mewtwo is weak against. Mewtwo might be able to get in one or two hits, but Arceus' type changes would also mean that Mewtwo's attacks would hit at low or zero damage.
Mewtwo is a clone of Mew. While Mewtwo’s savagery and raw strength might give Mew a run for its money, this little Legendary from Gen 1 still manages to come out on top. During their battle in the first movie, for instance, Mew seemed to have fun the entire time they were fighting. This suggests that if Mew were going full force it wouldn’t be much of a competition. Furthermore, Mew has the DNA of all Pokémon inside its body, allowing it to transform into any other living creature —
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