In the TCGs Base Set, Mewtwo didnt quite reach the obscene power level that this cloned Pokemon did in the mainline games, but it is still quite a powerhouse under the right circumstances
Ultra Sun: If you try too hard to get close to it, it won't open up to you
If the creature doesn't meet any of the above exceptions and can attack, it must attack a player other than the controller of the spell or ability that goaded it if able
Sealed Shining Fates is increasingly hard to find, putting upward pressure on graded singles
You can just make the most powerful play that you can find with your own cards, and you dont have to consider the risk of things going wrong
He is a 9000-power blocker who, on play, can activate a Dressrosa type Event directly from your hand, which counts toward Lucys draw condition and makes your sequencing both efficient and flexible