I think if you want to talk about true power, you'd study Mao. But if you wanted to talk about benefit for one's country while wielding said power? You'd look at Stalin. Hitler is not the absolute caricature "they" (not just talking about Jews) have made him into, but nor is he all that successful, as tyrants go.

Of course, a true patriot would discard all three and go with Roosevelt (Teddy or Franklin, both were badass).