Weak toBugGhostDark ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	AstonishShadow Ball	26.1
Pheromosa	BugFighting	Bug BiteBug Buzz	25.2
Darkrai	Dark	SnarlShadow Ball	23.5
Chandelure	GhostFire	HexShadow Ball	23.3
Gengar	GhostPoison	LickShadow BallLegacy	23.3
Absol	Dark	SnarlBrutal SwingLegacy	22.8
Eternatus	PoisonDragon	Poison JabDynamax CannonLegacy	22.3
Dragapult	DragonGhost	AstonishShadow Ball	22.2
Hoopa	PsychicGhost	AstonishShadow Ball	21.8
Lunala	PsychicGhost	Shadow ClawShadow Ball	21.8
Gholdengo	SteelGhost	HexShadow Ball	21.8
Zoroark	Dark	SnarlFoul Play	21.7

Fog boosts the Ghost attacks above. Windy boosts Mew.

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

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

Questions people ask

What is Mew weak to in Pokémon GO?

Mew takes 1.6 times from Bug, Ghost and Dark.

What's the best counter to Mew?

Blacephalon with Astonish and Shadow Ball, worth 26.1 damage per second against Mew's own defense. The full ranking is above.