Quora is pretty much unreadable now. Is the main answer just chat gpt? That's how it seems from mobile view. The page is too noisy to navigate for me.

So a 500m is roughly a couple thousand or ten thousand times more than a Hiroshima nuke?

This would wipe out an area equivalent to a mid sized country and would possibly have global effects. The threshold for that is somewhere between 250 meters and a kilometer but we fortunately do not have any data to make that much more precise. You definitely wouldn't shrug your shoulders and get on with life, it would be the most important event in your life assuming it didn't end. Depending on where it happened the economic impact of such an incident would destabilize the world economy for decades.