Weak toBugGhostDark ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	AstonishShadow Ball	49.8
Pheromosa	BugFighting	Bug BiteBug Buzz	48.0
Darkrai	Dark	SnarlShadow Ball	44.8
Chandelure	GhostFire	HexShadow Ball	44.4
Gengar	GhostPoison	LickShadow BallLegacy	44.4
Absol	Dark	SnarlBrutal SwingLegacy	43.5
Eternatus	PoisonDragon	Poison JabDynamax CannonLegacy	42.5
Dragapult	DragonGhost	AstonishShadow Ball	42.4
Hoopa	PsychicGhost	AstonishShadow Ball	41.6
Lunala	PsychicGhost	Shadow ClawShadow Ball	41.6
Gholdengo	SteelGhost	HexShadow Ball	41.5
Zoroark	Dark	SnarlFoul Play	41.4

Fog boosts the Ghost attacks above. Windy boosts Duosion.

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

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

Questions people ask

What is Duosion weak to in Pokémon GO?

Duosion takes 1.6 times from Bug, Ghost and Dark.

What's the best counter to Duosion?

Blacephalon with Astonish and Shadow Ball, worth 49.8 damage per second against Duosion's own defense. The full ranking is above.