Rampant Rejuvenator

Ramp packaged as a body, with the payoff deferred until the creature is gone. It arrives sized at 2/2 (a pair of counters on the printed 0/0 doing the work), and on death fetches up to its power in basic lands straight onto the battlefield. That timing is the whole design: it turns every death-based removal spell, every chump block, every sacrifice outlet into an Explosive Vegetation that drew you a blocker first. Green has always paid for its acceleration with a fragile creature (Sakura-Tribe Elder is the archetype, dying by choice to fetch a single land), but here the death trigger scales rather than settling for a fixed one-for-one, and it counts power as of the moment the creature left the battlefield. That last point is the deckbuilding gate. Because the trigger reads power from last known information, the swelling has to happen while the creature is alive, not after it dies: there's no way to pile on counters once it's died, since it's no longer on the battlefield to receive them and the game already recorded the power the instant it left. Build it up first (extra counters, a doubling effect), then sacrifice it at its peak, and the land haul reflects whatever it was worth when it died. The restraint holding the rate together is the pairing of the death gate with the basic-only clause: lands arriving already untapped and on the battlefield is a stronger effect than tutoring to hand, so both conditions carry real weight on a four-mana card. A Sakura-Tribe Elder whose reward grows in proportion to how badly you wanted it dead, provided you paid to grow it while it still lived.