It's interesting that you would declare Brutus to be a bad leader, because I think there is more textual evidence that point to him being a good leader than a bad one. Indeed, Brutus is an honorable man who loves both Rome and Caesar, but who is drawn into the conspiracy to kill Caesar against his will in an attempt to protect the representational government of the Roman state. As such, I would advise you to consider arguing that Brutus is a good leader.
A couple of quotes support this evaluation of Brutus. One occurs in Act 2, Scene 1, in which Brutus receives a fake letter from the citizens of Rome looking for his help:
'Brutus, thou sleep'st. Awake, and see thyself.
Shall Rome, etc. Speak, strike, redress!
Brutus, thou sleep'st; awake!' (46-8)
This quote displays a Roman populace in peril (or, to be more accurate, the appearance of a Roman populace in peril; the letter itself is a forgery), and it is the force that finally moves the reluctant Brutus to join the conspiracy to kill Caesar. As such, he will only act violently if he thinks it necessary to protect the people of Rome.
Another good quote occurs during Brutus' funeral speech in Act 3, Scene 2, in which Brutus declares that "Not that I lov'd Caesar less, but that I lov'd Rome more" (22-3). In making this claim, Brutus says that he didn't kill Caesar because he hated Caesar; rather, he killed Caesar to protect Rome from an autocrat.
All in all, these quotes show Brutus to be a rather good leader: he's selfless, cares deeply about his countrymen, and will only use force when absolutely necessary. As such, I would suggest you use these quotes to explore the notion of Brutus as a good leader.