Give a Pokemon a single move that instantly makes them OU. No abilities, not more than one move, just a single move that would potentially make them OU.

Hard Mode: No Shell Smash.

>Pic related gets Parting Shot.

I just want my favorite Pokemon to be OU again. The fairy typing gave it a nice big amount of resistances, but I still don't think it's enough. With Parting Shot, it'd be the ultimate momentum keeper between taunting, encoring, and reducing attack and special attack.