Suggest me a book where a nightmare spreads it’s wings

I want to read a story where something minor or even benign becomes a nightmare overnight.

For example “Carrie” by Stephen King is good for this. But “Firestarter” also by King is even better, because this is a gone horribly right situation. They wanted her to start the fire. Akira is also very good.

But I kind of want it worse. I want the skies to go dark and entire continents wiped out because of a relatively minor decision that spirals out of contol very very quickly.

Like maybe you want somebody good to do a bad thing *once*. But deep inside they were a monster all along, and they did not know it yet. And now nothing can stop them.

Or maybe you want to improve your chances in a struggle by summoning the bigger fish. But the bigger fish is so terrible that the entire struggle that you were in becomes insignificant. It is just much much worse than you could have imagined.

Something like that.

by HuntOld2852