>>20547325>Altaria @ Altarite252 HP 252 SpDef
-Roost
-Dragon Dance
-Return
-Earthquake
Creating an undying Cotton Guard tank is just asking to die from Toxic, esp. since you lose Natural Cure upon Mega-evolving.
Cotton Guard + Hyper Voice is the weakest combo because of that reason. It can't boost its stats, and the most threatening thing that set can do is use Toxic, which is ineffective against Poison and Steel type mons, the two mons who resist your unboosted Hyper Voice.
When you have a bulky mon as Altaria with its new defensive typing, you can treat it like Multiscale Dragonite: you can guarantee stat boosts (esp. since big Attaack/SpAttack boosts guaranteed by mega) to enable sweeps.
Dragon Dance is the perfect setup skill, ameliorating its poor Speed and boosting its mega-boosted Attack. From there, you just choose Return for a STAB stronger than Hyper Voice (substitute aside) hitting at 203 base power after STAB, and Earthquake for coverage, hitting the Steels and Poison types that resist.
Roost is for healing, since you'll inevitably be able to deal with the chip damage on mons you decide to setup on, and to help ease against revenge priority you may survive given your bulk. It also allows you to attempt early boosts to pose a threat, then come in later to heal and then prepare for lategame sweep.
