Frozen Solid

Two effects bolted into one Aura, and the join is what gives the package its bite. The first clause does nothing the turn it lands; it bites only later, freezing the creature in whatever state it ends the turn, so a tapped attacker can never rotate back into combat. The second clause is where the freeze gets teeth: any damage at all, from a stray Shock, an unfavorable block, a single ping, destroys the creature outright. That converts the enchanted permanent from a parked threat into a liability for its controller, who can no longer block or trade with it without handing you the kill, and cannot untap it back into the fight. The design problem it resolves is the chronic weakness of disabling Auras, which only buy time and let the creature keep doing its job from one side of the board: here the time-buy comes packaged with an execution method, so a deck already throwing damage around supplies the second half itself. The cost of the package is everything that haunts enchantment-based control: a single Disenchant-style answer frees the prisoner with nothing gained, anything that grants the creature an untap effect on its own terms slips the freeze, and an untapped creature that simply takes no damage sits there untouched, neither tapped down nor killed. Removal that hands you the trap but asks you to spring it.