Weak toBugGhostDark ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	AstonishShadow Ball	26.5
Pheromosa	BugFighting	Bug BiteBug Buzz	25.5
Darkrai	Dark	SnarlShadow Ball	23.8
Chandelure	GhostFire	HexShadow Ball	23.6
Gengar	GhostPoison	LickShadow BallLegacy	23.6
Absol	Dark	SnarlBrutal SwingLegacy	23.1
Eternatus	PoisonDragon	Poison JabDynamax CannonLegacy	22.6
Dragapult	DragonGhost	AstonishShadow Ball	22.5
Hoopa	PsychicGhost	AstonishShadow Ball	22.1
Lunala	PsychicGhost	Shadow ClawShadow Ball	22.1
Gholdengo	SteelGhost	HexShadow Ball	22.1
Zoroark	Dark	SnarlFoul Play	22.0

Fog boosts the Ghost attacks above. Windy boosts Mega Alakazam.

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

Mega Alakazam's moveset, stats and CP All counters Raid board

Questions people ask

What is Mega Alakazam weak to in Pokémon GO?

Mega Alakazam takes 1.6 times from Bug, Ghost and Dark.

What's the best counter to Mega Alakazam?

Blacephalon with Astonish and Shadow Ball, worth 26.5 damage per second against Mega Alakazam's own defense. The full ranking is above.