Weak toFlyingFirePsychicIce ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	IncinerateMind BlownLegacy	48.2
Mewtwo	Psychic	ConfusionPsystrikeLegacy	41.5
Reshiram	DragonFire	Fire FangFusion FlareLegacy	40.0
Salamence	DragonFlying	Fire FangFly	36.9
Chandelure	GhostFire	Fire SpinOverheat	36.6
Moltres	FireFlying	Fire SpinFly	36.3
Cinderace	Fire	Fire SpinPyroball	36.1
Volcarona	BugFire	Fire SpinOverheat	35.7
Darmanitan	Fire	Fire FangOverheat	35.6
Yveltal	DarkFlying	GustOblivion WingLegacy	35.5
Alakazam	Psychic	ConfusionPsychicLegacy	35.4
Toucannon	NormalFlying	PeckBeak BlastLegacy	35.2

Clear boosts the Fire attacks above. Clear and Overcast boost Gloom.

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

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

Questions people ask

What is Gloom weak to in Pokémon GO?

Gloom takes 1.6 times from Flying, Fire, Psychic and Ice.

What's the best counter to Gloom?

Blacephalon with Incinerate and Mind Blown, worth 48.2 damage per second against Gloom's own defense. The full ranking is above.