Rumbling Slum

The price for a 5/5 at four mana is paid every single turn, and the card itself collects it: one damage to each player, you included, on the upkeep before you ever swing. That self-inflicted clock is the whole conceit. A symmetric pinger that costs both players equally would just be filler; the design twist is that the damage is yours to recoup. You are the aggressor, so you set the race, and a 5/5 closes a game far faster than a one-point upkeep tax burns through your own twenty. The body has to be oversized precisely because the ability is a liability: if the creature were merely good, the ping would make it bad, so it has to be a beating that the slum's own grumbling can't quite undercut. It is a design built for the deck that was already planning to win before its own life total mattered, where the shared damage closes both ends of the gap and the green-red colors point you straight at the fast curve that gets there first. Left to stall, it kills you on schedule, which is the honest cost of putting a 5/5 in front of you for four. Few creatures wear their downside this plainly, and fewer still make it the engine of the threat rather than a footnote to it.