Ammit Eternal

A 5/5 with afflict 3 for three mana is a rate too good to print without a leash, and the leash here is unusually clever: the body sheds a -1/-1 counter's worth of stats every time an opponent casts a spell, then snaps back to full only when it lands a hit on a player. That clause turns the card into a referendum on tempo. Sit back and the opponent can pile counters faster than you can attack, whittling a beater into a token; force damage through and the reset wipes every counter at once, returning it to 5/5 and re-arming the threat for next turn. The afflict trigger compounds the pressure, since blocking it still costs the defender three life, so even a chump that absorbs the attack pays a toll. The real tension is who controls the clock: the controller wants to attack into open mana, daring the opponent to spend spells and shrink it, while the opponent wants to hold up cheap interaction precisely to keep it small enough to trade away in combat. Crucially, the reset only fires on combat damage dealt to a player, so chumping it to keep it shrunk is a legitimate plan: the defender eats three life from afflict but denies the snap-back. Most self-shrinking creatures simply rot under their own drawback; this one ties its recovery to connecting, which makes shoving it into combat both the win condition and the only way to undo the damage opponents do to it.