Ruin Explorer
Legend
I mean, just in the early 1490's the Sword Coast alone faces at least five potential existential threats to civilization...and they haven't even finished with that slice of time and space yet.
First off, we should discount everything that happens "off-screen", i.e. between editions. None of that is a real threat, it's just an excuse to shake things up. Second off, none of it ever happens outside of that! It's always like "OH NO BAD THINGS COULD HAPPEN!" and then they don't. You can only cry wolf so many times before you need to burn Cormyr to the ground to prove that the wolf actually exists.
The only thing I can think of, off-hand is at the beginning of Descent into Avernus when they blow up Elturel, but then it's hilarious because none of the characters seem to take it particularly seriously and also the whole thing is written like it's a small place (which is weird because in 2E it was massive). So they undermined even that!