Jace, the Mind Sculptor

Four loyalty abilities, and three of them would each be worth printing on their own card. That is the design that earned the planeswalker its reputation as the high-water mark of the type. The +2 functions as a Fateseal lock against an opponent's draw step, denying resources while building toward the ultimate. The 0 is the part that broke the math: a card-advantage and card-selection engine that fills your hand, then tucks the two cards you least want onto the top of your library where the next draw is already accounted for, all without spending loyalty, so it loops every turn the planeswalker survives. The -1 is tempo and protection in one, bouncing the creature that would otherwise attack it down. The -12 is the rare ultimate that actually ends games rather than threatening to. The trouble was that the floor never matched the ceiling: even when an opponent pressured it, Brainstorm-on-a-stick at zero loyalty meant the card was never dead, only deferred. That refusal to ever be a bad draw is what made it the most powerful planeswalker for a long stretch and what got it banned in Modern, a status it held until Wizards judged the format fast enough to punish a four-mana do-nothing turn. The lineage of "card advantage that also stalls the board" runs through plenty of designs since, but none have given a single permanent this many ways to be the best card in any hand.