Marc Antony in Julius Caesar by William Shakespeare  proved himself to be a loyal friend.  He found the assassination of Caesar abhorrent.  Marcus Antonius [Marc Antony} was a great general under Julius Caesar and one of his closest friends. He was also a distant relative of Caesar.  As a young man, Marc Antony did not always make good decisions; and so he was sent to Greece to study rhetoric.

Obviously, his natural oratory ability and his study of the Greek orators helped him to win over the people of Rome and influence others to trust him.  While serving with Caesar, Antony showed a fine aptitude for command, distinguishing himself with both courage and leadership.  Later, Antony would become Caesar's most trusted and able general. Unfortunately, his brutish and overbearing personality created problems that would plague Antony throughout his life.

When Caesar was assassinated, Antony swore vengeance for him.  In his famous funeral oration, Antony convinced the Roman citizenry through his ability to manipulate that the assassins were murderers of the greatest Roman who had ever lived.  At the end of his oration, the people were ready to tear the conspirators into shreds.

But were I Brutus,
And Brutus Antony, there were an Antony
Would ruffle up your spirits and put a tongue
In every wound of Caesar that should move
The stones of Rome to rise and mutiny.

And the mob was off to find the assassins.

His popularity with the Romans and the other Senators enabled Antony to become a part of the new triumvirate with Lepidus and Octavius Caesar, the nephew of Julius Caesar.  Eventually, Marc Antony would gather an army together and hunt down the two remaining conspirators.  Before he could return them to Rome to be tried, both Brutus and Cassius killed themselves.  

By late in 44 BC, Antony pushed through several laws, scattering the assassins throughout the provinces, and used his command of Caesar's former legions to maintain control. Antony procured the Gallic provinces for himself.

Antony was able to see into the hearts of men.  He knew that Brutus had been a part of the conspiracy because he believed that Caesar would become too powerful.  That is why when he finds the body of Brutus, he gave him the ultimate compliment from one man to another: This was a man.

As shown in Act V of Julius Caesar, Octavius was not going to allow Antony to bully him into submission.  On more than one occasion, Octavius chose to go against the orders of Antony.  After returning to Rome, Octavius would try to gain the inheritance of Julius Caesar since Caesar had no real heirs.  Lepidus and Antony joined forces and faced off against Octavius.  After several battles, Antony’s armies are defeated. Octavius becomes the new Caesar.

What were the defining qualities of Antony?

Intelligent, shrewdness, military savvy, personable, great orator, logical, loyal to Caesar, kept his word, and ambitious

Antony has gone down in history as a loyal friend to Caesar but also a great general who was brought down by an Egyptian queen, Cleopatra.  Of course, that is a story for another time.