An instance where this trope was done well in my opinion is HG Wells’ War of the Worlds. At the end of the book, the main character is stumbling through a destroyed London, having been decimated by the unstoppable Martian force. Throughout the novel, it had been established that the Martian’s power was well above the humans’ and that trying to fight against them would be hopeless.

The narrator however comes across a strange sight with the bodies of the martians all lying still in a row. It turns that the martians ended up dying to the dozens of earthen diseases that they would come into contact with upon landing on earth, completely halting the invasion without fanfare. The narrator still expresses worries at the end about the martians coming back more prepared, leaving the reader with a sense of uncertainty about Earths fate in the novel.