The answer is:
First, Octavius and Mark Antony's conflict exhibits Mark Antony's intensifying vanity. For example, when his determination that Lepidus is unsuitable of his position, it creates a dissent between Octavius and Mark Antony, which advances through the play and leads to the final fall of the Roman Republic.
As regards Brutus and Cassius' distinct integrity values, Brutus blames Cassius for taking bribes and doubts whether Caesar's death was ineffective. Their rivalry also emphasizes the ruin of their friendship, a central archetype of the Roman Republic.