Altaria @ Life Orb
Trait: Natural Cure
120 HP / 252 SAtk / 136 Spd
Nature: Modest
-Draco Meteor
-Fire Blast
-Hidden Power Ground
-Roost
XPower SwapX
252+ SpA Life Orb Accelgor Bug Buzz vs. 120 HP / 0 SpD Altaria: 84-99 (26.16 - 30.84%) -- guaranteed 4HKO
252+ SpA Life Orb Altaria Fire Blast vs. 4 HP / 0 SpD Accelgor: 377-445 (124.83 - 147.35%) -- guaranteed OHKO
252+ SpA Life Orb Altaria Draco Meteor vs. 4 HP / 0 SpD Accelgor: 329-387 (108.94 - 128.14%) -- guaranteed OHKO
With Accelgor only 4HKOing Altaria while being swiftly 1HKO'd in return by either of Altaria's attacks, I think that Altaria is a very strong counter to Accelgor. Even with Stealth Rock (didn't use it in the calc as the other team doesn't have it right now) it's only 3HKO's, meaning it can still easily Roost off any damage that Accelgor may try to inflict and KO in response. Regardless, it's versatility in smashing anything that comes in with a Draco Meteor and then screwing any special attacker with Power Swap is something that can't be underestimated, meaning that it can force more switches and give it more opportunity to Roost or just continue to smash faces. Plus it's ability, Natural Cure, means it can be a very good status sponge as it can't be worn down by Toxic or crippled by Paralysis or Sleep.
I'd like some clarification on the Hidden Power of choice though, as if Nidoqueen does get banned after this pick and HP Rock comes into play Altaria loses it's ability to counter Accelgor, being 2HKO'd with or without rocks. Basically, is Hidden Power Water set in stone or could it be changed depending upon the status of Nidoqueen?
Edit: After discussion changed Power Swap to HP Ground, due to Power Swap depending more based on surprise which really won't be a factor in this match with both sides knowing the others team, and HP Ground being another solid attacking option that gives Altaria very good coverage in the tier.