>>15468440>Mega Mawile>OPKeep in mind that she's slow and doesn't have great special bulk (base 50 HP is shit). If you can take the Sucker Punch, she's done.
252+ SpA Life Orb Hydreigon Fire Blast vs. 252 HP / 4 SpD (custom): 346-408 (113.81 - 134.21%) -- guaranteed OHKO
(yes, this factors in 110 power)
Or you can trap her with Magnezone and deal a ton of damage with T-bolt, especially with Specs.
Oh, and when Heatran comes back she's just plain fucked.