[breh]

Since I'm far too lazy to figure out anything (and Meganium is taken), I'll go with Bronzor.

Bronzor @ Eviolite
Bold Nature
252 HP / 200 Def / 56 SpD
-Rest
-Sleep Talk
-Calm Mind
-Hidden Power Ice

Torterra doesn't threaten Bronzor very much at all (has a chance at 4HKO; does hit harder when in Overgrow but it'll kill itself before you due to LO recoil and recoil) and Altaria's Draco Meteor is a 4HKO. Hidden Power Ice doesn't hit very hard, but does OHKO Altaria once fully boosted (meaning it can't stall out Bronzor with Rest).