Stinging Hivemaster

Toxic pays out on a delay: the poison counter is a wound that has to be revisited, not damage that resolves the game on contact, which is why the mechanic tends to want a stream of bodies rather than one big swing. This one solves that problem by dying well. Trade it in combat, chump it into a blocker, or feed it to a sacrifice effect, and the pressure survives the loss as a Phyrexian Mite that carries its own poison counter on the attack. The Mite can't block, which is exactly the point: it isn't a defender, it's a replacement attacker whose only job is to keep stacking counters, and it slides under a lot of the removal that would have answered the original 3/2. The effect is a threat that resists poison's natural counterplay, which is to trade with the toxic creatures and reset the clock. Kill it and the clock keeps ticking; ignore it and it swings for real damage plus a counter. That stacked pressure (a toxic attacker now, a smaller toxic attacker after it dies) is what buys an aggressive poison shell the resilience it needs to grind an opponent to ten poison before they stabilize.