Antony is shrewd and calculating, he is also a flatterer. He constantly calls Brutus an honourable man throughout his speech to the public, and even has his servant call Brutus a valiant and honourable man. Brutus is a bad judge of character, and very gullible, Antony works this to his advantage and soon Brutus is agreeing to let Antony speak at Caesars funeral, against Cassius's wishes. In the first scene, Antony tells the conspirators that he is a friend of theirs and that he supports their decision to kill Caesar, as he too believes that Caesar was a tyrant that could not be stopped any other way. This of course, is not true as Antony has always been loyal to Caesar. This looks like Antony has befriended the conspirators, but in reality he is plotting to seek revenge and take over Rome, which illustrates to us how calculating and shrewd Antony is.
Before Antony goes up to the pulpit to make his speech, Brutus says "You shall not in your funeral speech blame us". Antonys speech, though it is full of sarcasm and hate for the conspirators, technically does not break Brutus's rule. This wordplay shows how great an orator Antony is. Antony repeats over and over in his speech that Brutus is an honourable man. The effect of this repetition is that the crowd begins to question this statement that they previously thought was fact. Brutus told the plebians that Caesar was ambitious, and would not benefit Rome, but Antony asked rhetorical