Adolph Hitler, in my opinion.
He took a downtrodden nation, completely stripped of everything that could possibly sustain it...and turned it into a global super-power that could have easily held off the united might of several countries, by itself. American and British governments both agree that if Hitler hadn't have gone after Russia, he would have made the war last several more years, if not win it entirely.
Not to mention he was a flawed person, so all in all an ordinary man with an extraordinary ability to lead. If you look past the bad things he's done, you get a man who wasn't a Saint, he wasn't a Villain. He was just a man who had a dream, and sought to earn this dream in any way he possibly could.
To quote Harry Potter like the geek I am: "He did many great things. Terrible! Yes...but great."
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My second choice, however...would be Abraham Lincoln. That man was a living saint. I do wonder how the United States would be if he had lived through his term as President.