What is one characteristic trait of Brutus from Act 5?

In light of Roman military ethics, it can be argued that Brutus was both courageous and honorable. We can also say that he was noble.
Brutus was raised as a Stoic by his uncle, Cato the Younger, who vigorously opposed the rule of Julius Caesar. In temperament, Cato was both unyielding and implacable; he certainly impressed upon Brutus the need to battle compromise in all areas of life.
In Roman military culture, every good warrior sought glory on the battlefield; there, his physical prowess was tested, and he was immortalized by his courageous acts. To retain honor, the Roman warrior needed a strong will and the energy to succeed. As a stoic, Brutus maintained iron control over his emotions; he was self-sufficient and self-possessed. The Stoics believed that destructive emotions (such as anger or anxiety) crippled the psyche and had to be brought under the control of the will. Thus, a man's character was defined by his ability to navigate perilous challenges without complaint. The Stoics called this pursuit of virtue man's greatest objective in life; an honorable man endured all for the common good, as Brutus believed he did.
Brutus' opposition to Julius Caesar was based on his strict moral code; he felt that Caesar's ambitions threatened the Roman state and the freedom of its citizens. So, Brutus fought to save the Roman republic, and he endured the atrocities of the battlefield in order to secure the common good. However, his limited focus fueled his naivety, and he failed to recognize the duplicity of the conspirators. In the end, Brutus was defeated in battle, and in line with his honorable character, chose to fall upon his own sword. In dying this way, Brutus expended his complete being for the good of the Republic. His sacrificial actions allowed him to exert one last control over his body and emotions; in his eyes, he retained his masculine courage and honor to his last breath. 
Hint: If you're looking for pictures that characterize Brutus as honorable, try picking examples from search engines that match pictures of warriors with words describing the warrior code of honor. 
Source:
Roman Honor: The Fire in the Bones by Carlin A. Barton.