Weak toPoisonSteel ×1.6

Attacker	Type	Moveset	DPS
Eternatus	PoisonDragon	Poison JabSludge Bomb	116.8
Metagross	SteelPsychic	Bullet PunchMeteor MashLegacy	114.7
Tinkaton	FairySteel	Fairy WindGigaton HammerLegacy	111.5
Naganadel	PoisonDragon	Poison JabSludge Bomb	110.8
Lucario	FightingSteel	Force PalmMeteor MashLegacy	108.9
Nihilego	RockPoison	Poison JabSludge Bomb	105.2
Roserade	GrassPoison	Poison JabSludge Bomb	102.8
Dialga	SteelDragon	Metal ClawIron Head	101.5
Munkidori	PoisonPsychic	Poison JabSludge Bomb	100.9
Regigigas	Normal	Hidden PowerCrush GripLegacy	99.6
Genesect	BugSteel	Metal ClawMagnet Bomb	99.2
Revavroom	SteelPoison	Poison JabGunk Shot	96.9

Overcast boosts the Poison attacks above. Overcast and Partly cloudy boost Igglybuff.

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

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

Questions people ask

What is Igglybuff weak to in Pokémon GO?

Igglybuff takes 1.6 times from Poison and Steel.

What's the best counter to Igglybuff?

Eternatus with Poison Jab and Sludge Bomb, worth 116.8 damage per second against Igglybuff's own defense. The full ranking is above.