No man has yet been able to rule the world, but people have gotten close. The British Empire was once the largest empire in all the world. They controlled 23% of the worlds population and 24% of the land at their peak. During WW2 they had 2.9 million soldiers fighting to save their homeland.
Although many would say God, this is an inaccurate answer due to the fact that God is a supernatural being and not a human.
I hope this helps! :)