Weak toPoisonSteelIceFairy ×1.6

Attacker	Type	Moveset	DPS
Tinkaton	FairySteel	Fairy WindGigaton HammerLegacy	24.2
Eternatus	PoisonDragon	Poison JabSludge Bomb	23.6
Metagross	SteelPsychic	Bullet PunchMeteor MashLegacy	23.1
Naganadel	PoisonDragon	Poison JabSludge Bomb	22.4
Enamorus	FairyFlying	Fairy WindDazzling Gleam	22.4
Kyurem	DragonIce	Steel WingGlaciateLegacy	21.9
Lucario	FightingSteel	Bullet PunchMeteor Mash	21.4
Nihilego	RockPoison	Poison JabSludge Bomb	21.2
Zacian	FairySteel	Metal ClawPlay Rough	20.8
Roserade	GrassPoison	Poison JabSludge Bomb	20.8
Tapu Koko	ElectricFairy	Quick AttackNatures MadnessLegacy	20.6
Dialga	SteelDragon	Metal ClawIron Head	20.5

Overcast boosts the Poison attacks above. Overcast and Windy boost Mega Altaria.

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

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

Questions people ask

What is Mega Altaria weak to in Pokémon GO?

Mega Altaria takes 1.6 times from Poison, Steel, Ice and Fairy.

What's the best counter to Mega Altaria?

Tinkaton with Fairy Wind and Gigaton Hammer, worth 24.2 damage per second against Mega Altaria's own defense. The full ranking is above.