My god, Aggron is a defensive monster. A nightmare for every physical attacker ever. Mega Medicham's 4x effective Drain Punch struggles to 2HKO this thing. I don't have any particular movesets, but EV spread I would say goes like this for a pure Defensive Megaggron 252 Spdef/Def (Depends if you already have a good wall on your team of a certain type.) 252 attack, and 4 speed. Also, try out a baton pass strategy with this thing. Speed Boost Scolipede plus a few swords dances, baton pass to Aggron, mega evolve and you win.