The "It Almost Happened" Disaster Movies

Since Hollywood was born, heroes saved the people from disasters in movies. No matter if it comes to bombs, asteroids, floods or warfare, there were always heroes who kept us safe. We concentrated on mostly fictional or at least strongly dramatized scenarios without mainly intelligence services' actions. Superheroes are also left out, because there are so many of them and after their actions, people mostly always have to build up the planet completely again, which is also a catastrophe. Spoilers ahead!

Which of them is the best scenario of getting into trouble and solving it?

Please inform us of your local hero here.