Career
Marcus Antonius served under Caesar in Gaul, commanded the left wing at Pharsalus in 48 BCE, and was consul in 44 when Caesar was assassinated. His funeral speech and his handling of the aftermath made him the leading Caesarian.
With Octavian and Lepidus he formed the Second Triumvirate in 43 BCE, a formally constituted commission with the power to reorder the state. The proscriptions that followed killed several hundred senators and equestrians, Cicero among them. At Philippi in 42 BCE the triumvirs defeated the assassins.
In the division of responsibilities Antony took the east. He formed a political and personal alliance with Cleopatra VII of Egypt, campaigned against Parthia with heavy losses, and reorganised the eastern provinces and client kingdoms.
Actium
Relations with Octavian broke down through the 30s BCE in a propaganda war Antony lost decisively. Octavian obtained and published a document he presented as Antony's will, and framed the coming conflict as a war against a foreign queen rather than a civil war between Romans.
At Actium in 31 BCE Antony's fleet was blockaded and broke out with partial success. His army surrendered within days. He and Cleopatra died in Alexandria the following year.
The reputation, and who wrote it
Almost everything about Antony reaches us through the tradition the winner established. The portrait of a capable soldier ruined by drink and by an Egyptian queen is Augustan, and it was elaborated by poets writing under Augustus's patronage.
Plutarch's Life, written a century and a half later, is the fullest account and is more sympathetic than the Augustan version while still working within its moral frame. Cassius Dio is later still.
This does not mean the charges are false. It means the evidence is a prosecution case, and the platform reads it as one. The specific claims that can be checked against other evidence — the Parthian losses, the territorial arrangements in the east, the political settlement with Cleopatra — indicate a competent administrator making a coherent if unsuccessful bid for power, not a man undone by infatuation.