Mewtwo

The former king of Pokemon Go, Mewtwo's stats and moveset options are strong enough that it once persuaded trainers to take off work and pursue EX eligible gyms for a chance at capturing the Genetic Pokemon. And this is with good reason; on release, it was the single strongest thing in the entire game, and defined the concept of a generalist, especially when it had access to the seldom-resisted and high-powered Shadow Ball, and even more after it was later given access to Ice Beam, Thunderbolt, and Flamethrower. And while power-creep has ensured that Mewtwo is no longer the absolute-top-must-have Pokemon, it's still an extremely valuable Pokemon, and one of the absolute top Pokemon in the game when a Psychic weak Raid Boss shows up.

Best PvE Offensive Moveset

Confusion is the Fast Move of choice in neutral scenarios or when Psychic is Super Effective. Psycho Cut works best when Psychic is resisted or the target has a double-weakness to Mewtwo's non-Psychic Charged Move, and is easier to dodge with.

• Confusion with Psystrike makes Mewtwo one of the objectively strongest things in the entire game, and is this Pokemon's biggest claim to fame. Psycho Cut has lower damage, but it allows for an easier time with dodging.
• Flamethrower, Ice Beam, Thunderbolt, Focus Blast, and Shadow Ball* should pair with Psycho Cut or Confusion for the situations listed above. When in doubt, just default to Psycho Cut due to its higher energy generation and easier dodging.
• Hyper Beam* is an easy-skip, and Return* should be TMed away... but please don't purify your Shadow Mewtwo.

Psycho Cut gives Mewtwo the ability to use its charged moves faster, which is better suited for its squishy nature, whereas Confusion hits much harder through shields.

Psystrike is Mewtwo's cheapest charged move at 45 energy, and an extremely powerful one too, especially considering it benefits from STAB. Shadow Ball is as powerful as ever, and hits for widely unresisted damage. Focus Blast then covers any Normal-types that would resist Shadow Ball, and it nukes the numerous Steel-type threats, though it takes quite a long time to charge. Ice Beam has the same energy cost as Shadow Ball and offers extra coverage against Flying- and (non-Ghost or Steel) Dragon-types instead. Flamethrower and Thunderbolt have less relevant coverage and aren't as efficient.