Scenarios involving "No Hiter" or "No Stalin" or also "No Mao" have been proposed quite a number of times. But, what would the 20th century look like without all of it's three principal thugs? So my idea is, in one way or another, all three are killed in this TL long before they can assume power in their respective countries.
What happens now?
(Note: I'm well aware that they all were born before 1900, but since this is primarily focused on the 20th century, I decided to post it in the after 1900 section)