Large-scale environmental catastrophes

I'll give just one. The eruption of Mount Tambora in 1815 was one of the volcanic eruptions with widespread damage. Mount Tambora erupted, bringing thermal waves and tsunamis that killed 38,000 people (estimated). It is not just the tsunami and thermal waves, but also the ash plume that caused a cool down on the earth's atmosphere by 5°C causing "The Year Without Summer" and caused crops worldwide to fail, or degrade causing famine. That is all I know :) have a good day.