[Some Fat Guy in L.A.]

Tambora might be the most powerful and destructive volcanic event of the past 2 millennia.

Thought Thera was bigger?

[gleeaikin]

Thera was closer to 3 1/2 millennia ago. Suspect more like Krakatoa in size. Also the 535 event(s) may have been greater. For 535 ad his link suggests Ilopongo in Central America among other interesting ideas including Krakatoa.

https://en.wikipedia.org/wiki/Extreme_weather_events_of_535%E2%80%93536