10. Lucy Stillman (Assassin's Creed)
I was really shocked with this plot twist near the end of Assassin's Creed: Brotherhood. Lucy was a character who has been with Desmond from the very beginning and they even had this budding love story going on. However, it was cut short before it even started when Desmond stabbed her beyond his control.
We later found out that this was because Lucy was secretly working for the Templars. I was truly heart broken over this.
