I'm inclined to say Woodrow Wilson or FDR. I know that's American-centric. WW initiated the League of Nations...saved Europes ass the first time, and initiated the Federal Reserve. FDR was a major force in saving the World's ass, got rid of gold/silver as a monetary basis in the US and all the social programs and international programs he willingly/unwillingly started.
I don't agree with all the programs and initiatives started by the 2, but they had the greatest influence in such a wide array of ways. Social, militarily, political and economically. Name 2 other men who achieved so many influential policies.