Weak toFightingRockGrassElectric ×1.6

Attacker	Type	Moveset	DPS
Regieleki	Electric	Lock OnThunder CageLegacy	25.4
Lucario	FightingSteel	Force PalmAura SphereLegacy	22.8
Zeraora	Electric	Volt SwitchPlasma Fists	21.9
Kartana	GrassSteel	Razor LeafLeaf Blade	21.8
Zekrom	DragonElectric	Charge BeamFusion BoltLegacy	21.4
Xurkitree	Electric	Thunder ShockDischarge	21.1
Pheromosa	BugFighting	Low KickFocus Blast	20.9
Terrakion	RockFighting	Double KickSacred SwordLegacy	20.8
Blaziken	FireFighting	CounterAura Sphere	20.6
Breloom	GrassFighting	Force PalmGrass KnotLegacy	19.6
Glimmora	RockPoison	Rock ThrowMeteor Beam	19.3
Rampardos	Rock	Smack DownRock Slide	19.1

Rainy boosts the Electric attacks above. Rainy and Snow boost Cloyster.

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

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

Questions people ask

What is Cloyster weak to in Pokémon GO?

Cloyster takes 1.6 times from Fighting, Rock, Grass and Electric.

What's the best counter to Cloyster?

Regieleki with Lock On and Thunder Cage, worth 25.4 damage per second against Cloyster's own defense. The full ranking is above.