Hellkite Charger

The promise is a loop, not a beating. Aggressive Dragons usually sell themselves on the body and the evasion, and the 5/5 flier with haste is a fine clock on its own. But the attack trigger is the actual engine: pay the cost once and you untap every attacker for a second combat phase, pay it again in that phase and you can chain a third, a fourth, as far as your mana stretches. Each repeat untaps the whole attacking team, so the Dragon scales with whatever else swung alongside it rather than just doubling its own swing. The price is the governor on the loop: you need a real mana engine to extend it, which turns the card from a finisher into a payoff for ramp, untap effects, and cost reduction, less a free Aggravated Assault stapled to a body than a tax on every extra phase you want. The window matters too. Because the trigger fires on attack and the extra phase arrives after combat, you are committing the payment before blocks, betting that the additional swings are worth more than the mana. In a deck that can generate enough red to keep buying phases, it stops being a Dragon that attacks and becomes a Dragon that simply does not stop attacking until the table is empty or the mana runs out.