If you own an English-language Pokemon B/W game, you can obtain a free Level 70 Mewtwo over Wi-Fi! He knows the moves Psystrike, Shadow Ball, Aura Sphere and Electro Ball, and is holding a King's Rock. He is available until either the 26th of February or the 6th of March.

can you it if you didnt finish the game?

I believe you can, but you can always beat the game in a day or two.

You can, my brother got it today. Also, lol, I got this earlier today. It's pretty cool, tbh.

Too bad B/W suck.

Ah overpowered mewtwo. What was nintender thinking? We need a psyduck event! Lol jk.
FYI: psystrike is a more powerful version of psyshock, a special move that hits the targets defense.