Brutus is written to be a complex character and a tragic hero. He is complex in his own right, a powerful public figure, a husband, a master, a respected military leader and a trusted friend of Julius Caeser. During his many soliloquies to the insight of his motives, we learn that he is always in conflict with his own decision, the hindsight of his own decision and the regret of the ones he failed to take. So, why does Brutus commit suicide? You know when he finished his assassination, he ponders whether killing a friend is worth it for the greater good of his country, noble or just selfish, a failure for his own beliefs. He is idealistic, being one of his greatest flaws, his own ambition dominate every other motivation. This naive idealism led to miscalculation that brings a chain of effects that led Rome to the civil war. He refuses to kill Mark Antony when he killed Caesar, then he let Mark Antony speaks to the crowd during Caesar funeral oration, which Mark Antony to rally the crowd against Brutus. The only way he could repay for all the error he made is only by killing himself, which he did.