Charizard EX

Charizard is the avatar of raw power in Pokemon TCG Pocket. While it takes a lot of setup, its tremendous synergy with Moltres EX means that it has the time to stew on the bench and build up energy while its best-bird-friend gets everything ready. When it's done and ready to go, Charizard EX can literally one-hit KO any Pokemon in the game reliably, making it an extremely frightening force when it leaves the bench. In fact, there's literally no way in the game for a Pokemon to survive a Crimson Storm from Charizard EX aside from keeping it from being used.

A Charizard EX deck needs a fair bit of setup and time, so it can be preyed on by some faster decks, but it's also one of the best archetypes at keeping itself safe until it's ready to begin crushing the opposition. So long as you get all of the cards that you need relatively early, this can be a very hard deck archetype to contend with.