Maimonides
Emperor
I'm surprised nobody mentioned 1492 in Spain:
-The Inquisition was born.
-Columbus made his 1st voyage to the Americas.
-The last Muslims in Iberia were defeated.
-The large Jewish population of Spain was converted or expelled.
-Spain was united under a single monarchy.
Each of those points had a huge impact on world history. Taken together, 1492 Spain must be the biggest turning point during the OP's time period.
-The Inquisition was born.
-Columbus made his 1st voyage to the Americas.
-The last Muslims in Iberia were defeated.
-The large Jewish population of Spain was converted or expelled.
-Spain was united under a single monarchy.
Each of those points had a huge impact on world history. Taken together, 1492 Spain must be the biggest turning point during the OP's time period.