1. He had a conscience. Expressed doubt.
2. Thought he was doing what was best for the empire. Seeing Rome's history of tyrants, it is understandable that Brutus would think Caesar could've been another Sulla.
3. Committed suicide, an honorable act in Roman society. Then it was not perceived as cowardliness, but rather as a way for a man to maintain their honor in life.
1. Easily swayed by powerful, charismatic men.
2. Didn't consider all sides of the situation, as Caesar was actually helping Rome.
3. Propagated the corruption of the Roman Senate and paid for it.
4. Betrayed the trust of what was thought to be a friend. Julius Caesar perceived Brutus as loyal, as loyalty is one of the grandest of Roman virtues (Client/Patron system).
5. Gave up too easily, committing suicide.