Weak toPoisonGhostSteel ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	AstonishShadow Ball	24.1
Eternatus	PoisonDragon	Poison JabSludge Bomb	22.5
Metagross	SteelPsychic	Bullet PunchMeteor MashLegacy	22.1
Chandelure	GhostFire	HexShadow Ball	21.5
Tinkaton	FairySteel	Fairy WindGigaton HammerLegacy	21.5
Gengar	GhostPoison	LickShadow BallLegacy	21.5
Naganadel	PoisonDragon	Poison JabSludge Bomb	21.4
Dragapult	DragonGhost	AstonishShadow Ball	20.5
Lucario	FightingSteel	Bullet PunchMeteor Mash	20.4
Nihilego	RockPoison	Poison JabSludge Bomb	20.3
Hoopa	PsychicGhost	AstonishShadow Ball	20.1
Lunala	PsychicGhost	Shadow ClawShadow Ball	20.1

Fog boosts the Ghost attacks above. Overcast and Windy boost Mega Gardevoir.

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

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

Questions people ask

What is Mega Gardevoir weak to in Pokémon GO?

Mega Gardevoir takes 1.6 times from Poison, Ghost and Steel.

What's the best counter to Mega Gardevoir?

Blacephalon with Astonish and Shadow Ball, worth 24.1 damage per second against Mega Gardevoir's own defense. The full ranking is above.