DrunkenlySober t1_j73595u wrote

The scariest disasters are known as mass extinction events. There have been 5 in the history of the earth. These disasters add numerous species to the extinction list

The last one was 66 million years ago and killed 75% of all species. The gap between these events has been as short as 20 million years and as long as 130 million years

The scariest of these events is an asteroid collision. Hard to detect, can happen out of nowhere, and absolutely devastates the earth including very extended environment changes