That One Attack/Video Games/Tower Defense

Examples of That One Attack in Tower Defense games include:

Plants vs. Zombies has Dr Zomboss' desperation attack, in which he drops a caravan onto six of your plants, instantly squashing them. Unlike most of his other moves, this one cannot be avoided in any way possible. Thankfully, it is predictable (he only uses it once he is below half health, immediately after he gets back up from attacking).
The Destroyer from Mini Robot Wars merges two of Dr Zomboss' attacks and cranks it up to eleven. Its deadliest move has it open its mouth and fire out a Wave Motion Gun at two of your rows. Sure, you can move a few of your minirobots out of the way, but this attack will most likely destroy any non-defensive unit in the area of effect. Worst of all, this attack comes out without warning, unlike Dr Zomboss' caravan!