Not Stat Value, not BST; Base Stat.
Mega Mewtwo X
Shuckle and Mega Aggron
Special Attack- 194
Mega Mewtwo Y
Special Defence- 230
Mega Mewtwo X and Mega Mewtwo Y
Hope I helped :)
The highest base stat of any individual Pokemon is Blissey's 255 HP. One day we might see something break that, but we'll have to wait and see now.
Hope I helped.
Oh look, a Pokemon with higher HP: http://th04.deviantart.net/fs71/200H/i/2013/303/d/e/mega_evolution_blissey_by_idaida-d6qcvt8.jpg MEGA BLISSEY :DDDDDDDDDD