Weak toFightingGroundFireWater ×1.6

Attacker	Type	Moveset	DPS
Blacephalon	FireGhost	IncinerateMind BlownLegacy	21.3
Lucario	FightingSteel	Force PalmAura SphereLegacy	18.0
Reshiram	DragonFire	Fire FangFusion FlareLegacy	17.7
Pheromosa	BugFighting	Low KickFocus Blast	16.5
Terrakion	RockFighting	Double KickSacred SwordLegacy	16.4
Blaziken	FireFighting	CounterAura Sphere	16.3
Chandelure	GhostFire	Fire SpinOverheat	16.2
Cinderace	Fire	Fire SpinPyroball	15.9
Volcarona	BugFire	Fire SpinOverheat	15.8
Darmanitan	Fire	Fire FangOverheat	15.7
Inteleon	Water	Water GunHydro CannonLegacy	15.6
Kyogre	Water	WaterfallOrigin PulseLegacy	15.5

Overcast boosts the Fighting attacks above. Clear and Snow boost Mega Steelix.

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

Mega Steelix's moveset, stats and CP All counters Raid board

Questions people ask

What is Mega Steelix weak to in Pokémon GO?

Mega Steelix takes 1.6 times from Fighting, Ground, Fire and Water.

What's the best counter to Mega Steelix?

Blacephalon with Incinerate and Mind Blown, worth 21.3 damage per second against Mega Steelix's own defense. The full ranking is above.