Diancie @ Leftovers
Ability: Clear Body
EVs: 252 HP / 4 Atk / 252 SpD
Sassy Nature
- Heal Bell
- Diamond Storm
- Stealth Rock
- Moonblast
This thing is an absolute monster. Already, it's a lead, and since Accelgor is usually a lead [especially if they're running Spikes] it can already get itself in with Accelgor in a lead vs lead scenario. While already being capable of getting in when Accelgor is on the field, it can also switch in to any move Accelgor has.
252 SpA Life Orb Accelgor Giga Drain vs. 252 HP / 252+ SpD Diancie: 99-117 (32.5 - 38.4%) -- 1.5% chance to 3HKO after Leftovers recovery
252 SpA Life Orb Accelgor Energy Ball vs. 252 HP / 252+ SpD Diancie: 117-138 (38.4 - 45.3%) -- guaranteed 3HKO after Leftovers recovery
252 SpA Life Orb Accelgor Focus Blast vs. 252 HP / 252+ SpD Diancie: 77-91 (25.3 - 29.9%) -- 0% chance to 4HKO after Leftovers recovery
252 SpA Life Orb Accelgor Bug Buzz vs. 252 HP / 252+ SpD Diancie: 43-51 (14.1 - 16.7%) -- possible 9HKO after Leftovers recovery
252 SpA Life Orb Accelgor Sludge Bomb vs. 252 HP / 252+ SpD Diancie: 58-69 (19 - 22.6%) -- possible 6HKO after Leftovers recovery
Based on these calcs, Diancie can switch into absolutely any attack Accelgor has, take another one, and then OHKO with Diamond Storm. There is nothing Accelgor can do to avoid this, especially if they don't have Energy Ball. All they can do is switch out.
4 Atk Diancie Diamond Storm vs. 0 HP / 0 Def Accelgor: 440-518 (146.1 - 172%) -- guaranteed OHKO
All Accelgor can do is switch out. Diancie can come in at any time, take any attack Accelgor could possibly have, and OHKO under any circumstance while still being able to set up rocks and heal your team, making sure it's not useless against teams without Accelgor.
That's the definition of a
counter, right?