Rigby does some craters.
V̶o̶l̶u̶m̶e̶ ̶=̶ ̶P̶i̶ ̶x̶ ̶R̶a̶d̶i̶u̶s̶^̶2̶ ̶x̶ ̶D̶e̶p̶t̶h̶ ̶V̶o̶l̶u̶m̶e̶ ̶=̶ ̶3̶.̶1̶4̶ ̶x̶ ̶4̶.̶6̶6̶5̶6̶ ̶x̶ ̶1̶.̶0̶1̶ ̶M̶i̶n̶i̶m̶a̶l̶ ̶v̶o̶l̶u̶m̶e̶ ̶(̶s̶i̶n̶c̶e̶ ̶w̶e̶ ̶c̶a̶n̶'̶t̶ ̶s̶e̶e̶ ̶t̶h̶e̶ ̶e̶n̶t̶i̶r̶e̶ ̶d̶e̶p̶t̶h̶ ̶o̶f̶ ̶t̶h̶e̶ ̶c̶r̶a̶t̶e̶r̶)̶ ̶=̶ ̶1̶4̶7̶9̶0̶0̶0̶0̶c̶c̶ ̶ ̶I̶t̶'̶s̶ ̶p̶r̶e̶t̶t̶y̶ ̶c̶l̶e̶a̶r̶ ̶v̶a̶p̶o̶r̶i̶z̶a̶t̶i̶o̶n̶.̶ ̶2̶5̶7̶0̶0̶ ̶x̶ ̶1̶4̶7̶9̶0̶0̶0̶0̶ ̶=̶ ̶9̶0̶.̶8̶4̶ ̶t̶o̶n̶s̶,̶ ̶8̶-̶B̶+̶.̶
Scrap that, Psychomaster35 did a way better calc in the comments and the one i made is wrong anyways.
Have you tried the top-right crater? That seems to be the largest one. Also, I would recommend you use Pulverization values instead of Vaporization, as few bits of rock survived, but the rest is nowhere to be seen.
Rigby: 6 px/104.14 cm
Crater: 139 px/2412.57666667 cm (1206.28833334 cm for the radius)
Going by the hemisphere since we get a bad angle of the height...
((4/3)*pi* 1206.28833334^3)/2 is 3676308905.61 cm^3
Going by Pulverization...
3676308905.61*214.35 is 788016813918 joules/188.340538699331 tons, or Multi-City Block Level.
Hey, at least this is legit while the 8-A base forms are outliers (exept angry Benson)