There are other volcanoes, whose volcanic explosiveness index is 7 and 8. If they began to erupt at the same time, it would lead to the disappearance of most of the living creatures on the planet, including people.
In addition, as a result of such an eruption, aircraft that were previously in the air will begin to fall, buildings will collapse, and the power grid will fail. The ash will make drinking water poisonous, the temperature could eventually drop 15 degrees Celsius for six months, and acid rain will make farming impossible for the next decade.
