>>22699935There are lots of ways to run Mega Altaria. You can either use it as an offensive DD sweeper, a physical tank, special / mixed attacker, ect.
People say that it pairs really well with almost any Steel type, and this is mostly true. It works best on balance paired with Ferrothorn, Jirachi, or Heatran, for example.
The DD set is a great sweeper that packs a LOT of power. People say "base 110 Attack with no Life Orb sucks!" but Pixilate Return is a 130 base power move with no drawbacks, and makes up for the low-ish Attack. IMO using DD is kind of a waste of Altaria's potential, and its weakest set.
The defensive set (252 HP 252 +Def, Hyper Voice / Roost / Fire Blast / Heal Bell) provides a ridiculous amount of team synergy and support. It walls half of OU, and packs decent power behind its Hyper Voice (this set is a great answer to SubCM Keldeo). Altaria can be a bit of a status magnet, so Heal Bell is amazing on it. This set is great bacause it covers so much in one teamslot, and pairs well with lots of other mons.
The offensive set is one of my favorites. 252 HP / 252 Special Attack (maybe a few Speed EVs), Modest, Hyper Voice / Fire Blast / Earthquake / Roost or Draco Meteor. This set covers almost every check and switchin, OHKOing MegaZard X with Draco, 2HKOing Heatran with EQ, and every other Steel type with Fire Blast. This set makes for a very dangerous pivot, as it can win a large number of 1v1s, and retains a lot of the defensive set's bulk.
