What event is the greatest turning point in history?
The Neolithic Revolution was the greatest turning point
It began with a simple boycott of Jewish shops and ended in the gas chambers at Auschwitz as Adolf Hitler and his Nazi followers attempted to exterminate the entire Jewish population of Europe. For some is seen as a major event, not as a turning-point. For others the Holocaust was a turning point in history, which prompted the world to say "never again".
The turning point in Greek history is the fall of the Byzantine Empire. After this event, the Greeks lost everything they had before to the Ottomans. They stay for 400 years under the Ottoman Empire and in 25 Mars 1821 they won their independence. A major fact is that Greek kept their Orthodox religion and they didn't change it during the 400 years under Ottoman Empire.
The Bolshevik Revolution of 1917 was a major turning-point in history because nearly every major historical event that occurred afterwards was either caused by it or was affected by it in some distinctive way. In addition, the central historical tension in the 20th century's second half, the Cold War, can be directly traced back to the rise of the "Bolsheviks" in Russia in 1917.
A possible turning point would be that event that happens when the superhero begins to get the ultimate victory. Perhaps he feels that he is too weak and that all is lost. Then something happens that causes him to regather his courage and strength, and he gains the victory. That "something" is the turning point.
It was not so much a turning point in world history because he failed to reach Asia, but it was a turning point in the history of Native American tribes. He was the first European contact and with him came sickness, discrimination, death and a eventual loss of land. A way of life was lost on that day on Hispinola and the ripples of it still echo today.