He's not on your list, but my choice is
Gavrilo Princip, the assassin of the heir to the Austrian throne.
Get rid of him and WWI (probably) never happens.
No WWI and both Vladimir Lenin and Adolf Hitler are remembered, if at all, as nothing more than loud mouthed rabble rousers.
No Communism, no Nazism, no holocaust and probably no "American Century".
The world today would be unrecognizable.