Spawnwrithe

Trample is the whole engine, and the specific reason it works is that the body cannot be quietly walled off. A snowballing token-maker hiding behind flying or fear demands an answer in the air; this one only needs to push some damage past a blocker, and trample guarantees that even a chump dying to the first point still lets enough through to land the trigger. The first connection is cheap and survivable; the next is a doubling line that compounds every combat the controller can force damage through. None of it happens without combat damage to a player, so a true wall (a blocker big enough to eat the entire 2/2 with toughness to spare) or a Fog genuinely shuts the copy off: the threat scales with whether you can get through, not with raw mana. The detail that makes it durable is that each spawned creature is a full copy, ability included, so there is no central node to assassinate. Trade with the original and every 2/2 it left behind is still a fresh copy-engine the moment it connects. The danger lies in treating a small green body with a single keyword as a problem to handle next turn; ignore it for three turns and the math has gone exponential, and killing one copy resets nothing.