Weak toFightingRockSteelFire ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	IncinerateMind BlownLegacy	22.5
Lucario	FightingSteel	Force PalmAura SphereLegacy	19.1
Reshiram	DragonFire	Fire FangFusion FlareLegacy	18.6
Pheromosa	BugFighting	Low KickFocus Blast	17.4
Terrakion	RockFighting	Double KickSacred SwordLegacy	17.4
Blaziken	FireFighting	CounterAura Sphere	17.2
Chandelure	GhostFire	Fire SpinOverheat	17.1
Cinderace	Fire	Fire SpinPyroball	16.8
Volcarona	BugFire	Fire SpinOverheat	16.6
Metagross	SteelPsychic	Bullet PunchMeteor MashLegacy	16.6
Darmanitan	Fire	Fire FangOverheat	16.6
Kartana	GrassSteel	Fury CutterSacred Sword	16.4

Overcast boosts the Fighting attacks above. Snow boosts Regice.

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

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

Questions people ask

What is Regice weak to in Pokémon GO?

Regice takes 1.6 times from Fighting, Rock, Steel and Fire.

What's the best counter to Regice?

Blacephalon with Incinerate and Mind Blown, worth 22.5 damage per second against Regice's own defense. The full ranking is above.