Essentially through dropping the atom bomb on Hiroshima and Nagasaki. The Japanese soldiers had been fanatically loyal to the Emperor and fiercely defended the Pacific islands leading to heavy casualties amongst the American forces.
After the atom bomb was used Emperor Hirohito surrendered and Japanese soldiers followed his order to stop fighting.
The main reason why Cambodian genocide perpetrators have not been brought to justice are the incompetent and alleged corruption of the local tribunal court, and lack of support from international community as well as the death and sickness of several witnesses and perpetrators.
