Sevinne, the Chronoclasm Sevinne, the Chronoclasm works well because there are so many synergies surrounding it, like Secrets of the Dead and Torrential Gearhulk
Up to this point in the series, any time a Pokmon wanted to learn a new move, an old move would have to be forgotten, leaving that Pokmon unable to use it again without the help of a Move Relearner or TM to teach it back to them
6 Elesh Norn, Grand Cenobite The original version of the Mother of Machines herself, Elesh Norn can turn the tide of the game just by being in play
Cloud, Midgar Mercenary As the second coming of Stoneforge Mystic, Cloud, Midgar Mercenary is pretty powerful, allowing you to tutor for an equipment and have a toolbox at your disposal
Which let's face it, hardly happens
3 Blastoise (Shadowless) - Base Set Blastoise being one of the original starter evolutions perhaps makes it one of the more popular cards in the entire game