Many works have the Holy Hand Grenade: a purifying, holy blast of light and goodness which eradicates evil in sight, turning it into a dusty pile of ash. However, what happens if it gets reversed? The Unholy Nuke tends to be a power fit for a Big Bad or Complete Monster: a devastating magic/technique/ritual fueled by unholy power, often the Evil Counterpart to a technique used by the good guys. Usually it involves Black Magic and darkness, but other elements can play a role as well. Bonus points if it's Powered by a Forsaken Child. It may be a Dangerous Forbidden Technique. Sometimes an Evil Knockoff will use this as a dark mirror of one of the hero's own powers. In Video Games, expect to see it used by the Final Boss.