And then everyone got radiation poisoning and died. The end.
Cydone and Emu already did this to everyone. They detonated a total matter conversion bomb. By my calculations, it's equivalent to a 12 Megaton bomb, where ALL the energy was radiation, instead of the usual mix of heat, kinetic, and radiation.
A quick look up reveals atomic explosions are usually 15% radiation, so that's equivalent to a 80 megaton bomb. Right in the middle of everybody for their being irradiated* pleasure.
*Omega: Yet another thing I can do my Saitama impression for.