Nidoqueen was not banned, so accelgor will be using HP Water in this CCT.
Anyway, I really like the Altaria suggestion. May I recommend using Specs Altaria though? The Specs set still does a great job of countering Accelgor, but is much more powerful, and any team without a steel type(which is roasted by Fire Blast) or a specially defensive cryogonal or Slowking(which are weak to Pursuit)is going to lose a lot of health every time Altaria switches in(even off of that average special attack stat,a 140 BP move with specs is going to hurt pretty much anything offensive).
Here is the Specs set that imo is better than the Life Orb set, although both do have its advantages(LO can switch moves and has roost), the specs set hits so much harder, and it doesn't particularly matter when it comes to switching move because unless they have a steel type not named Durant or Aggron(which are 1HKO'd and 2HKO'd respectively), and then you can use Fire Blast.
Here is the specs set:
Altaria (F) @Choice Specs
Trait: Natural Cure
EVs: 252 Spa / 4 SpD / 252 Spe
- Draco Meteor
- Fire Blast
- Dragon Pulse
Thanks to natural cure, it can use rest, switch out and the sleep goes away, just if you were a bit confused.