Auron, Venerated Guardian

The trigger reads like a snowball, but the timing is what makes it lethal. Every attack grows Auron by a counter, and each growth exiles a defender smaller than his current power, so a 2/5 that swings unanswered climbs to a 3/6, banishes something, then a 4/7, banishes something larger, widening the net one swing at a time. The exile lasts only until Auron leaves the battlefield, which is the restriction paying for the rate: kill him and everything comes back at once, so the removal is real but rented. That temporary-exile clause does work white's harder answers usually reserve for permanent effects; here it trades permanence for repeatability, one creature per swing for as long as he lives. Vigilance is not filler on this shell. It means the attacks that build the counters do not cost you a blocker, so Auron can grow, strip a defender, and still hold the fort, which is the piece that turns a fragile attacker into a durable one-card advantage engine. The power-comparison target is the honest limiter: he can only exile things he already out-sizes, so the first swing picks off a small blocker and each subsequent counter widens the reach rather than letting him grab the biggest threat immediately. Because the whole engine fires on attack, it rewards the aggressor for committing to combat every turn, punishing decks that leave small creatures back to chump.