Answer:
US representative and chief prosecutor of the International Military Tribunal.
Step-by-step explanation:
Justice Robert H Jackson who was the US representative and chief prosecutor of the International Military Tribunal in 1945, was one among the many members of the international tribunal which was established to prosecute and punish WWII criminals.
When he said this quote, Justice Jackson meant that the crimes committed by the axis power, especially the Nazis, were so devastating that one could not simply ignore them. He further says that it was so devastating and horrifying that if it were to ever happen again, the world would not survive to see its end.