Instead of giant dinosaurs, giant mammals which are wiped out by an asteroid. Instead of human mammals, one ends up with lizard people living in the warm/hot countries of the world.
Ogadai Khan does not die when he did, Western Europe is destroyed and taken over by the Mongols temporarily.
Jesus's disciples are killed along with him, Christianity is strangled and never becomes a religion.
Disease in the Americas mainly affects the whites rather then the Native Americans, making it's conquest much harder.
No WW1 somehow, meaning no fascism/Nazism/Communism in power, and colonialism lasts longer-as does Anti-Antisemitism in Europe with no Holocaust to show what it leads to.
A Tsar as strict as Stalin, leading to a very unpleasant Tsarist state.
Hitler dies in early 1939, possibly stopping WW2 from breaking out.
MacAuther uses nukes in China in the Korean War.
Either a disused Chinese mine is not reopened in 2019, or some lab workers in China take proper precauations in their lab, and Covid 19 does not escape to cause injury, death and chaos all over the world.