Answer 1

The strongest that's actually in the BW2 Pokedex is Black Kyurem and White Kyurem, who have stat totals of 700.

Of course, you can get all the Pokemon by trading etc, and Arceus is still the strongest of all time at 720.

Comments

Black 2, Pokemaster.

Answer 2

Kyurem-B.
700 BST. That insane Attack. Reasonable defenses and Speed, and good Special Attack.