Rampaging Yao Guai

The X does double duty, and that is the whole design tension. Every point you pour in makes the body bigger through +1/+1 counters and simultaneously raises the ceiling on what the enter trigger can destroy: pay four and you arrive as a 6/6 that erases any number of artifacts and enchantments whose combined mana value sits at four or under. Green has always been the color that strips noncreature permanents on an ETB (Reclamation Sage, Acidic Slime, Bane of Progress); what is unusual here is that the removal budget scales continuously off the same X that builds the attacker, so the card doesn't destroy one permanent or all noncreatures indiscriminately but a targeted quantity capped by a value you choose. The counter is what governs the trade: because the removal budget and the creature's size share the same X, a big cleanup leaves you with a big attacker, and a cheap creature can only sweep cheap targets. There is no free scaling in either direction, which keeps a green blowout from being a pure removal spell that happens to leave a Grizzly Bears behind. Vigilance and trample point the finished creature squarely at offense: it clears the defensive furniture on the way in, then swings without dropping its guard.