One key event was his discovery of his true origin. Another was the burning of Nibelheim. Also, his battles with Cloud were very important in the story.
Firstly, Sephiroth's creation through Shinra's experiments is a fundamental part of his story. His discovery that he was created from Jenova's cells was a huge event that changed his path. His actions in Nibelheim, including the massacre and the burning, were key moments. Also, his encounters with Cloud, especially their final battle which was a battle between two different ideologies - Sephiroth's view of his 'destiny' and Cloud's will to protect the world - are among the key events in his full story.
The key events start with his existence as a top SOLDIER in Shinra. Then comes the revelation about his origin which was a turning point. After that, his destruction of Nibelheim is significant as it shows his descent into madness. And of course, his continuous attempts to gain control over the lifestream and his battles against the protagonists are crucial events in his story.
One key event is his discovery of his origin. Learning that he was created from Jenova's cells shatters his world view. Another is the burning of Nibelheim, which he does as part of his descent into madness. And of course, his final battle with Cloud and the other heroes is a crucial event.
The key events were the hijacking of the four planes, the two planes crashing into the World Trade Center towers, the plane hitting the Pentagon, and the fourth plane crashing in Pennsylvania.
One key event was Moses' birth when his people were slaves. His mother's clever plan to save him by putting him in the Nile was important. His life in the Egyptian court was a strange mix as he was of Hebrew origin. When he killed the Egyptian, it led to his exile in Midian. God's call to him in the burning bush was a turning point. The plagues that came upon Egypt were a big part of the story as they led to the Hebrews' freedom. And during their long journey in the wilderness, the receiving of the Ten Commandments on Mount Sinai was a defining moment for the Hebrews' faith and way of life.
One key event is the Battle of Stirling Bridge. Wallace and his men cleverly used the terrain to defeat the larger English army. Another is his capture. He was betrayed and handed over to the English. His execution was also a crucial event. It made him a martyr and inspired the Scots to keep fighting for independence.
The key events include the murder of his family which starts his journey. Then his training as an Assassin in Monteriggioni. His encounters with Cesare Borgia in Rome are also crucial.
One key event was the numerous escape attempts. Many prisoners tried to break out through tunnels. Another was the clever disguises used by some prisoners to try and blend in with the guards. Also, the discovery of some prisoners' secret workshops where they made tools for their escapes.
One key event is the murders committed by William Afton in Freddy Fazbear's Pizza, which led to the animatronics being haunted. Another is the constant struggle of the night guards to survive the nights against the possessed animatronics.
One key event is Nehemiah getting permission from the king. Another is his arrival in Jerusalem and assessment of the wall damage. Also, the organization of the people for the rebuilding work is important.
One key event is Guddu and Bablu's return. Another is the continuous power struggle within the Tripathi family. Also, the battles between the different gangs for control over illegal trades.
The key event is the Uchiha clan massacre. Itachi killed most of his clan members to protect the village from a possible coup. Another important event is his joining Akatsuki. And finally, his battle with Sasuke where he revealed the truth to him.