Weak toFlying ×2.56PoisonFirePsychicIceFairy ×1.6

Attacker	Type	Moveset	DPS
Enamorus	FairyFlying	Fairy WindFly	29.2
Yveltal	DarkFlying	GustOblivion WingLegacy	28.9
Toucannon	NormalFlying	PeckBeak BlastLegacy	28.6
Moltres	FireFlying	Wing AttackFly	28.5
Staraptor	NormalFlying	GustFlyLegacy	28.1
Rayquaza	DragonFlying	Air SlashHurricaneLegacy	26.3
Honchkrow	DarkFlying	PeckBrave Bird	25.6
Braviary	NormalFlying	Air SlashFly	25.6
Salamence	DragonFlying	Fire FangFly	25.5
Flamigo	FlyingFighting	Wing AttackBrave Bird	24.9
Tornadus	Flying	Air SlashHurricane	24.7
Blacephalon	FireGhost	IncinerateMind BlownLegacy	24.5

Windy boosts the Flying attacks above. Clear and Overcast boost Mega Chesnaught.

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

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

Questions people ask

What is Mega Chesnaught weak to in Pokémon GO?

Mega Chesnaught takes 2.56 times damage from Flying, and 1.6 times from Poison, Fire, Psychic, Ice and Fairy.

What's the best counter to Mega Chesnaught?

Enamorus with Fairy Wind and Fly, worth 29.2 damage per second against Mega Chesnaught's own defense. The full ranking is above.