Weak toGrass ×2.56

Attacker	Type	Moveset	DPS
Kartana	GrassSteel	Razor LeafLeaf Blade	40.5
Roserade	GrassPoison	Magical LeafLeaf Storm	34.5
Zarude	DarkGrass	Vine WhipPower Whip	33.9
Rillaboom	Grass	Razor LeafFrenzy PlantLegacy	33.5
Meowscarada	GrassDark	LeafageFrenzy PlantLegacy	32.7
Decidueye	GrassGhost	Magical LeafFrenzy PlantLegacy	32.2
Tapu Bulu	GrassFairy	Bullet SeedGrass Knot	32.1
Tsareena	Grass	Magical LeafGrass Knot	31.6
Sceptile	Grass	Bullet SeedFrenzy PlantLegacy	31.4
Ogerpon	Grass	Magical LeafGrass Knot	31.2
Breloom	GrassFighting	Bullet SeedGrass KnotLegacy	31.1
Xurkitree	Electric	Thunder ShockPower Whip	30.7

Clear boosts the Grass attacks above. Clear and Rainy boost Mega Swampert.

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

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

Questions people ask

What is Mega Swampert weak to in Pokémon GO?

Mega Swampert takes 2.56 times damage from Grass.

What's the best counter to Mega Swampert?

Kartana with Razor Leaf and Leaf Blade, worth 40.5 damage per second against Mega Swampert's own defense. The full ranking is above.