Because of the play’s emphasis on not having particularly wonderful or awful characters, there’s much more of a tendency to have characters that reflect each other’s qualities, good and bad, than ones that stand in direct contrast to each other. Lepidus’s desire to compromise and placate is compassionate in the view that Caesar and Antony are intransigent warmongers, but his traits are weaknesses if you think of Caesar and Antony as soldiers with convictions. Either way, he’s constantly portrayed as being unfit for his position of power. While Caesar and Antony might rule differently, there’s no disputing that either man would be a fit leader. You’re just not so sure with Lepidus.
Antony’s passion is a weakness compared to the clear purpose and deliberate steps Caesar takes. Both men pursue different paths to the same purpose of power. Sometimes, Caesar’s staunchness makes him appear like a stodgy calculating codger, especially at the banquet with Pompey, while the consequences of Antony’s profligacy occasionally make Caesar look like a sensible guy.
Octavia and Cleopatra, similar to Caesar and Antony, are two sides of the same coin. Cleopatra is passionate while Octavia is cool, but they both love Antony – just differently.