Top 4 Volcanic Eruptions (rated above 7 VEI)
Tambora, Indonesia 1815
Baitoushan, China-Korea border, about 1050
Kikai, Japan, about 4350 B.C.
Crater Lake, Oregon, USA, about 4895 B.C.

Top 10 Volcanic Eruptions in the World (Mattox S, volcano.und.edu)
1. Tambora, Indonesia 1815: VEI=7, 92,000 casualties
2. Santorini, Greece 1628 B.C.: VEI=6, unknown casualties
3. Krakatau, Indonesia 1883: VEI=6, 36,400 casualties
4. Santa Maria, Guatemala 1902: VEI=6, 6,000 casualties
5. Mount St. Helens, USA 1980: VEI=5, 57 casualties
6. Vesuvius, Italy 79: VEI=5, 3,360 casualties
7. Pinatubo, Philippines 1991: VEI=5, 932 casualties
8. Mount Pelee, Martinique 1902: VEI=4, 29,000 casualties
9. Nevado del Ruiz, Columbia 1985: VEI=3, 23,000 casualties
10. Unzen, Japan 1792: VEI=2, 15,000 casualties.

The volume of the Krakatau's eruption is estimated to be 18 cubic km, and Tambora's eruption is estimated to be 40 cubic km!