United States vs. Soviet Union
The Cold War produced some scary results. The decades-long conflict between the Soviet Union and the United States resulted in both sides owning the kind of arsenal that could unleash a sci-fi-level of apocalyptic devastation across the entire planet at the push of a red button.
On the flip side, the Space Race not only put a man on the moon, it inspired an entire generation to get interested in engineering, science, and whatever else it might take to defeat the Commies. More than anything else in the past century, it paved the way for major technological achievements—even if some of those achievements are terrifying.
Plus, those bombs never went off, but those sci-fi movies did get made. So there’s that.