From the utterly utterly addictive “TVTropes”
There are situations so bad that anything that would end them is justified. Anything. There is wisdom in facing a threat with a proportionate response. Sure, There Is No Kill Like Overkill, but it’ll likely cause a lot of avoidable collateral damage, and it’ll guarantee that tomorrow the next threat is stronger. But there are times when the threat is so great and things have gone so horribly wrong that there is no appropriate response. The situation is so dire that it justifies the use of any and every thing that might solve it, no matter how crazy, nonsensical, or horrific, regardless of cost or collateral damage. Things are at the point where even summoning Godzilla, king of monsters and patron saint of collateral damage, could not possibly make the crisis any worse. The situation has crossed the Godzilla Threshold. Once the Threshold is crossed, ANY plan, with even the smallest possibility of success, no matter how ludicrous, impossible, dangerous or abhorrent, suddenly becomes a valid option. This serves both narrative and authorial purposes. Suppose the heroes have an awesome weapon that nonetheless causes a lot of property damage, like a Kill Sat, or a captured or dormant monster. Or one knows a Dangerous Forbidden Technique that will put his life at risk. They have to use it, but it can’t be done lightly without portraying them as either careless or cruel. So the author contrives to make the situation call for its use in such clear terms the audience understands this was done as a last resort — and, if it’s handled properly, the audience doesn’t even notice.
If only there were an amazing song with a lyric “The blizzard of the world has crossed the threshold and its overturned the order of the soul…”