Weak toFightingGroundFire ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	IncinerateMind BlownLegacy	24.2
Lucario	FightingSteel	Force PalmAura SphereLegacy	20.6
Reshiram	DragonFire	Fire FangFusion FlareLegacy	20.1
Pheromosa	BugFighting	Low KickFocus Blast	18.8
Terrakion	RockFighting	Double KickSacred SwordLegacy	18.8
Blaziken	FireFighting	CounterAura Sphere	18.6
Chandelure	GhostFire	Fire SpinOverheat	18.4
Cinderace	Fire	Fire SpinPyroball	18.2
Volcarona	BugFire	Fire SpinOverheat	18.0
Darmanitan	Fire	Fire FangOverheat	17.9
Groudon	Ground	Mud ShotPrecipice BladesLegacy	17.3
Moltres	FireFlying	Fire SpinOverheat	17.1

Overcast boosts the Fighting attacks above. Snow boosts Registeel.

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

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

Questions people ask

What is Registeel weak to in Pokémon GO?

Registeel takes 1.6 times from Fighting, Ground and Fire.

What's the best counter to Registeel?

Blacephalon with Incinerate and Mind Blown, worth 24.2 damage per second against Registeel's own defense. The full ranking is above.