Weak toFightingGroundRockWater ×1.6

Attacker	Type	Moveset	DPS
Lucario	FightingSteel	Force PalmAura SphereLegacy	26.1
Pheromosa	BugFighting	Low KickFocus Blast	23.9
Terrakion	RockFighting	Double KickSacred SwordLegacy	23.8
Blaziken	FireFighting	CounterAura Sphere	23.6
Kartana	GrassSteel	Fury CutterSacred Sword	22.6
Inteleon	Water	Water GunHydro CannonLegacy	22.5
Kyogre	Water	WaterfallOrigin PulseLegacy	22.4
Glimmora	RockPoison	Rock ThrowMeteor Beam	22.1
Groudon	Ground	Mud ShotPrecipice BladesLegacy	22.0
Rampardos	Rock	Smack DownRock Slide	21.9
Conkeldurr	Fighting	Force PalmFocus Blast	21.8
Keldeo	WaterFighting	Low KickSacred Sword	21.6

Overcast boosts the Fighting attacks above. Clear and Fog boost Chi-Yu.

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

Chi-Yu's moveset, CP and shiny All counters Raid board

Questions people ask

What is Chi-Yu weak to in Pokémon GO?

Chi-Yu takes 1.6 times from Fighting, Ground, Rock and Water.

What's the best counter to Chi-Yu?

Lucario with Force Palm and Aura Sphere, worth 26.1 damage per second against Chi-Yu's own defense. The full ranking is above.