This trope is for any of those attacks that appear to do a ridiculous amount of damage, but on closer inspection actually have the rather strange effect of reducing one (or more) party members down to their very last Hit Point instead of inflicting normal (possibly lethal) damage. Lesser versions may not leave the target with strictly 1 HP, but relative to the scale of damage typically dealt in these battles, the end result is the same -- regardless of your character's HP beforehand, you are now on the threshold of Critical Existence Failure.