Yamamoto - assuming that he planned the attack at the insistance of the Emperor (General consensus AFAIK is that Yamamoto though attacking America was a bad idea) he planned an excellent strike. Very nearly a crippling blow.
Don't misunderstand me - attacking us was a colossal blunder. Had Japan not attacked, odds are that we would not have entered the war in time to save most of Europe. That being said, if the decision to attack were made by the Emperor, Yamamoto carried out his order to the best of his ability; the true mark of any great soldier.