Consecrated Sphinx

The asymmetry is the entire design: it punishes opponents for doing the most basic thing the game asks of them, which is draw a card. A 4/6 flying body already survives almost everything short of a hard sweeper, so six mana buys a durable threat before the text box does anything. Then the draw clause turns it into a soft lock. Every card an opponent draws (their natural draw step included) feeds you two, so even one opponent leaving it on the board for a full turn cycle hands you two extra cards minimum, and that floor multiplies fast wherever multiple draw steps answer to you. Any opponent running their own card-advantage engine is effectively paying double into yours. The pressure it creates is psychological as much as material, because the correct play against it is often to draw fewer cards than you want, which means it warps the opposing game plan even when it never fully fires. Older blue draw-engine creatures asked you to attack or tap mana; this one asks for nothing and works on your opponent's turn, on their dime, while you sit back. The cost is that it does nothing the turn it lands, leaves no value behind if it dies, and dies to any removal that clears six toughness. But the window between resolution and an answer is brutal, and one unanswered turn cycle usually decides the game.