Thundercloud Elemental

Both activated abilities cost the same , and both rewrite the board in service of the same goal: clearing the skies so a 3/4 flier can connect. The first taps every creature with toughness 2 or less, neutralizing the small chump-blockers and mana dorks that gum up a stalled board; the second strips flying from everything else, which is the line that actually closes games, since it leaves this Elemental as the only creature still in the air. Run both in a turn and you have an attacker swinging into a battlefield where nothing small can block and nothing tall can fly. The catch is the price tag: seven mana to deploy, then four more per activation, so the engine only matures in a deck with mana to burn and time to use it. That makes the body almost incidental to its function; a 3/4 is fragile for its cost, but the card is not trying to win a stat-line trade. It is a control-deck finisher, a single creature that converts a flooded mana base into a repeatable board-clearing assault, asking nothing of the rest of your deck except the lands to fuel it.