Celebi EX + Serperior

Celebi EX thrives on energy, so getting Lilligant out early to generate energy, and then having Serperior on the bench (you only need one, they don't stack) before Celebi EX hits the field can easily result in 10+ coin flips in just a few turns, which is more than enough to KO literally anything in the game more than 50% of the time on average.