Beast-Kin Ranger
The reward here is stapled to the thing green already wants to do: flood the board. Every creature that follows this one onto the battlefield hands it another point of power for the turn, so a wide development turns into a large attacker without any specific synergy piece doing the lifting. Trample is what converts that arithmetic into damage that lands: a 3/3 that swells each time you deploy another body threatens to punch through a chump block instead of being neutralized by it. The pump is temporary, so it never builds toward a permanent threat an opponent has to answer at leisure, and it fires only on your own creatures entering, which keeps it a beater rather than a self-fueling engine. Nothing about the trigger is locked to your main phase, either: because it fires whenever another creature enters, a flash body or an instant-speed token maker can inflate the Ranger mid-combat, after blockers are declared, to push a bigger chunk of damage than the defender was planning to eat. Nothing here is subtle, which is the point of a card built to anchor a go-wide green deck at common-adjacent stakes. This is the aggressive glue green has printed in one form or another for a long time: a body that gets meaningfully bigger the more you commit, asking you to keep the creatures coming rather than protect a single investment.
