I was wondering, are there any anime/manga where it is actually necessary to allow the ultimate evil to awaken? I'm not talking about a not-so-evil being like in a recent Demon King anime. I'm talking about a living death, a pure manifestation of doom and destruction; the sort of creature you usually don't actually see because the only way to win is to KEEP it from awakening.
An example might be a case in which such a creature's awakening is thought to be inevitable in the very distant future, and the only chance to stop it is to find some way to awaken it prematurely under circumstances that might just weaken it, or where its continued presence in eternal slumber is having some sort of effect, or perhaps its continued sealing requires a heavy price.
And it doesn't have to be definitively stated whether it's legitimately necessary for the beast to be freed if good is to win, so long as someone, good or bad, believes so and his argument is sound enough that it's a definite possibility.
There's plenty of stories out there where someone's trying to summon such a "god", but pretty much when this happens the ultimate villain is never seen because the good guys stop it from awakening, or if they don't stop it it's clearly a bad thing no matter how you slice it, and it's only through a desperate last gamble that they manage to stop it, often by returning it to sleep again rather than killing it.
I can only think of one such story off the top of my head that comes close to this scenario: