Nobody, I think this is an insane question.
So many different people had small impacts on humanity, most of it somewhat regional. Most of the heroes I could think of in Western countries will have had a very limited impact on Eastern history, and vice versa. Also, I am very sure nobody had only positive impact.
Another problem: not everybody will rate a certain impact equally as positive.
I'd suggest to remove focus and attention from god- or hero-like figures and shift it towards improvements won by community action.