Was the Japanese emperor Hirohito a puppet or a war criminal?
He can't have failed to notice that a war was being waged or that crimes were being committed in his name. Clearly he had the capacity to stop the war, which is what he duly did, if too late to stop the destruction of two cities. However the Japanese were rather better at getting rid of the evidence than the Nazis were. He escaped prosecution since it suited the Allies to keep him in a constitutional role, he belief he was the key to post war stability in Japan.
War criminal, he was intimately involved in the planning and execution of the war.
If he was a puppet, you would have to ask who the puppeteer was. If he was a war criminal, you would have to ask what crimes he personally committed. Depending on the answers you come up with, you may conclude that he was one, the other, both, neither, or some combination thereof.