Real manking geniuses

Mankind always moved forward when real genius showed up.

People like Socrates and philosophy; Tesla and technology; Einstein and classic physics; Hawking and quantum physics or astronomy; Beethoven and classic music; Hitler and his speech talent (whatever atrocities he did, you can't ignore his genius about his influence) etc.

It's obvious that there are tons of great minds in every age but real geniuses show up maybe once in a century.

Who do you think were the most important geniuses of mankind? Doesn't matter what they were so great at but it would be cool if you told us why you think so and what the person did.