Impelled Giant

The activation cost is the whole personality here: tapping your other red creatures isn't paying mana, it's spending the attack. Every creature you tap to pump this Giant is a body that won't be swinging, so the math is a deliberate trade between width and reach. Power, not the count of creatures, is what carries through, which means a single beefy red attacker can dump its whole punch into the Giant and let trample finish the job through a chump blocker. That trample clause is doing real work: without it, funneling all that power into a 3/3 just feeds a single block; with it, the redirected damage rolls over whatever stands in front. The design rewards a board built around one designated carrier rather than a go-wide swarm, an unusual incentive for a red creature, since red typically wants every body attacking at once. It works at instant speed during combat, so the pump can wait until after blockers are declared, turning the Giant into an ambush that reassigns your team's collective power onto one unblockable-by-math threat. The catch is the diminishing return on your own attack step: every creature you tap is one fewer source of combat damage, and a removal spell aimed at the Giant after you've committed leaves your tapped-down board exposed. A puzzle of a creature, built for players who'd rather concentrate force than spread it.