Anzrag, the Quake-Mole - 2RG
Legendary Creature - Mole God (Mythic)
Whenever Anzrag, the Quake-Mole becomes blocked, untap each creature you control. After this combat phase, there is an additional combat phase.
3RRGG: Anzrag must be blocked each combat this turn if able.
His claws tear at the foundations of civilization.
8/4
Anzrag will keep the damage from previous combats on the same turn. But there's no incentive to block it one creature at a time. If you can put enough power in front of it to kill it, you should do so immediately. If you can't, you're going to lose all your untapped creatures, and shortly thereafter, the game.
I guess there will be times when you can just take the eight damage (plus whatever other attackers are coming in) and then win on the backswing, but I doubt that'll be the most common scenario.