I would nominate Mary, Queen of Scots, as one of the most overrated historical figures. She has been called a Catholic martyr and she certainly suffered a lot during her life. Her father died shortly after her birth. She was raised away from home at the French court where she was treated like a princess and eventually married her first husband, the young French prince. Tragically, the prince died shortly after their marriage. Mary then returned to Scotland where she wasn’t warmly welcomed. Mary was cousin to Elizabeth, Queen of England.
Mary and Elizabeth had a fierce rivalry over the years because Mary was a Catholic and claimed to be the legitimate queen. Elizabeth was a Protestant and didn’t recognize Mary’s claim to the throne. After the Scots ousted Mary from Scotland, she asked for help from Elizabeth but Elizabeth put Mary in the Tower Of London for about 19 years and she was eventually executed for plotting against Elizabeth. So she is famous for all the wrong reasons, in my opinion.