re: In your opinion, who was the greatest leader in history?

Hitler was a terrible leader. Less than half of Germany actually voted for him as chancellor. Also, because of the way he reordered the command structure of the military his generals had overlapping authority and were constantly infighting with each other. Also, personally inserted himself into military decisions overriding the authority of some of the world's best tacticians and ordering them to do things like wasting countless lives and resources trying to take Stalingrad even though it was of no tactical significance. Hitler simply wanted to take the city with stalin's name on it for vanity. Let's not also forget that he was such a great leader that his own officers spent almost a year trying to kill him. The military achievements of Germany were in spite of hitler not because of him.