Articuno @ Heavy-Duty Boots
Ability: Pressure
EVs: 248 HP / 236 SpD / 24 Spe
Calm Nature
IVs: 0 Atk
- Roost
- Defog
- Freeze-Dry
- Heal Bell
Articuno is a counter. Because of it taking not too much from Qwilfish, it can switch into Liquidation or Poison Jab and threaten massive damage with Freeze-Dry. Even if the Qwilfish is faster (and the sample set for this Qwilfish isn't optimal, because it's from Centiskorch era), Pain Split will almost always never be enough to avoid a 2HKO from Freeze-Dry. Articuno can then Defog away the Spikes, and heal away any status it received.
0 Atk Qwilfish Liquidation vs. 248 HP / 0 Def Articuno: 88-105 (22.9 - 27.4%) -- 58.9% chance to 4HKO
0 SpA Articuno Freeze-Dry vs. 252 HP / 0 SpD Qwilfish: 236-278 (70.6 - 83.2%) -- guaranteed 2HKO