Complex sentence: Trained by the Assassins, Ezio starts killing those responsible for his family's murder, but over the years changes from a mere vigilante into the new leader of the Assissin's Order, and defends their ideals all over the world.
Split into simpler sentences: Trained by the Assassins, Ezio begins killing those responsible for his family's murder. Over the years, Ezio changes from being a mere vigilante, to the new leader of the Assassin's Order, defending their ideals all over the world.