Weak toBugGhostGrassElectricDark ×1.6

Attacker	Type	Moveset	DPS
Regieleki	Electric	Lock OnThunder CageLegacy	25.2
Kartana	GrassSteel	Fury CutterLeaf Blade	21.7
Zeraora	Electric	Volt SwitchPlasma Fists	21.6
Blacephalon	FireGhost	AstonishShadow Ball	21.4
Zekrom	DragonElectric	Charge BeamFusion BoltLegacy	21.1
Xurkitree	Electric	Thunder ShockDischarge	20.9
Pheromosa	BugFighting	Bug BiteBug Buzz	20.7
Darkrai	Dark	SnarlShadow Ball	19.3
Chandelure	GhostFire	HexShadow Ball	19.1
Gengar	GhostPoison	LickShadow BallLegacy	19.1
Absol	Dark	SnarlBrutal SwingLegacy	18.7
Roserade	GrassPoison	Magical LeafLeaf Storm	18.4

Rainy boosts the Electric attacks above. Rainy and Windy boost Mega Slowbro.

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

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

Questions people ask

What is Mega Slowbro weak to in Pokémon GO?

Mega Slowbro takes 1.6 times from Bug, Ghost, Grass, Electric and Dark.

What's the best counter to Mega Slowbro?

Regieleki with Lock On and Thunder Cage, worth 25.2 damage per second against Mega Slowbro's own defense. The full ranking is above.