Weak toBugGhostDark ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	AstonishShadow Ball	29.8
Pheromosa	BugFighting	Bug BiteBug Buzz	28.8
Darkrai	Dark	SnarlShadow Ball	26.8
Chandelure	GhostFire	HexShadow Ball	26.6
Gengar	GhostPoison	LickShadow BallLegacy	26.6
Absol	Dark	SnarlBrutal SwingLegacy	26.0
Eternatus	PoisonDragon	Poison JabDynamax CannonLegacy	25.4
Dragapult	DragonGhost	AstonishShadow Ball	25.4
Hoopa	PsychicGhost	AstonishShadow Ball	24.9
Lunala	PsychicGhost	Shadow ClawShadow Ball	24.9
Gholdengo	SteelGhost	HexShadow Ball	24.9
Zoroark	Dark	SnarlFoul Play	24.8

Fog boosts the Ghost attacks above. Windy boosts Mewtwo.

Level 40, 15 attack IV, costed against Mewtwo's own defense and typing, one per evolution family.

Mewtwo's moveset, CP and shiny All counters Raid board

Questions people ask

What is Mewtwo weak to in Pokémon GO?

Mewtwo takes 1.6 times from Bug, Ghost and Dark.

What's the best counter to Mewtwo?

Blacephalon with Astonish and Shadow Ball, worth 29.8 damage per second against Mewtwo's own defense. The full ranking is above.