The answer is: Honor and ambition
In Shakespeare's "Julius Caesar," the conspirators assassinate Caesar on the grounds that he is too ambitious. Caesar is indeed an extremely powerful ruler whose authority is represented by his words alone. In fact, Brutus is even more ambitious because he murders him to gain power, even though he later justifies Caesar's death appealing to the fact that he has always been considered a man of honor and that he wished the citizens of Rome to be free.