Rasputin
Rasputin may have been a con man, but he did give the Romanovs exactly the right advice on the biggest issue of their lives: Don't go to war with Germany. What if they'd taken his advice?
This isn't as flashy a way of stopping or delaying the Great War as saving Franz Ferdinand, but it has a better chance of delaying the blowup longer. Serbia is going to keep on provoking Austria-Hungary, so a Third Balkan War is going to happen. What turns it into the Great War is Russian support for Serbia. If the Tsar won't extend this support as far as war, the Third Balkan War happens in the Teens or the Twenties.
Other possible features of Reality Rasputin:
- Troubles in Ireland: There actually was an incipient uprising in Ireland by protestants in protest of the new Home Rule bill. Without the Great War, Ireland gets a different version of its civil war.
- Mussolini stays pacifist and Socialist.
- Hitler decides to give America a try, and ends up as one of Disney's top animators.
- Lenin stays in Zurich long enough to get shot by a mistress he didn't get to in our history.
- Igor Sikorsky remains in Russia, and develops working helicopters by the early Thirties.
- With no cheap surplus Jennies available from WWI production, there is no barnstorming era in the US. Charles Lindbergh and James Doolittle both become famous race car drivers. (Eddie Rickenbacker was already a famous race car driver.)