Flameblast Dragon

Most fatties of this kind put their threat on the body and stop there: a 5/5 flier closes a game in four swings and asks nothing more of you. The attack trigger rewires that math. Because it fires when the dragon attacks and the payment scales with X, every combat doubles as a Fireball pointed wherever you need it: a blocker that would have traded, a planeswalker ticking toward its ultimate, a player already low enough that the swing in the air finishes the job. The constraint that keeps it off the bomb pedestal is the trigger itself; the dragon has to survive a turn, untap, and commit to combat before the ability comes online, so the damage is a reward for keeping a six-mana creature alive rather than a removal spell stapled to a body. The sequencing cuts in the controller's favor more than it looks: once the dragon has been declared as an attacker, the trigger is already on the stack, and killing the dragon in response no longer stops the burn (the controller still pays on resolution). An opponent who wants to deny the damage outright has to answer the dragon during the beginning of combat step or earlier, before the attack is declared. Tapping low to clear the board on your turn hands you a clean window to dump excess mana into reach. It is a mana sink that turns a fair top-end threat into an inevitability engine, where flooding out reads less like a misfortune than a plan.