Weak toPoisonSteel ×1.6

Attacker	Type	Moveset	DPS
Eternatus	PoisonDragon	Poison JabSludge Bomb	98.0
Metagross	SteelPsychic	Bullet PunchMeteor MashLegacy	96.3
Tinkaton	FairySteel	Fairy WindGigaton HammerLegacy	93.6
Naganadel	PoisonDragon	Poison JabSludge Bomb	93.0
Lucario	FightingSteel	Force PalmMeteor MashLegacy	91.4
Nihilego	RockPoison	Poison JabSludge Bomb	88.3
Roserade	GrassPoison	Poison JabSludge Bomb	86.3
Dialga	SteelDragon	Metal ClawIron Head	85.2
Munkidori	PoisonPsychic	Poison JabSludge Bomb	84.7
Regigigas	Normal	Hidden PowerCrush GripLegacy	83.6
Genesect	BugSteel	Metal ClawMagnet Bomb	83.3
Revavroom	SteelPoison	Poison JabGunk Shot	81.3

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

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

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

Questions people ask

What is Jigglypuff weak to in Pokémon GO?

Jigglypuff takes 1.6 times from Poison and Steel.

What's the best counter to Jigglypuff?

Eternatus with Poison Jab and Sludge Bomb, worth 98.0 damage per second against Jigglypuff's own defense. The full ranking is above.