The core piece of information Octavian weaponized against Mark Antony was Antony's will. The article notes that the most "damning part" of the will was Antony's request to be:
Buried with Cleopatra in Egypt. This was factually true.
A violation of Roman custom, as it was forbidden for a Roman nobleman to marry a foreigner. This fact confirmed the violation of social and legal norms.
An indication that Antony viewed Alexandria, not Rome, as the center of his power and legacy, threatening Roman national pride.
Octavian (later Emperor Augustus) did not leak the will to inform the public; he did so with the specific intent to incite rage and political harm against his rival. This malinformation was used to:
Weaponize Nationalism: By exposing Antony's wish to be buried in Egypt with a foreign queen, Octavian framed Antony as a traitor who had abandoned his Roman identity.
Instigate War: The leaked will made the Roman Senate and populace believe Antony was forming a rival government in Egypt, turning a political rivalry into a popular clamor for war against Cleopatra and Antony.
Justify Damnatio Memoriae: The campaign successfully justified the later formal act of Damnatio Memoriae (damnation of memory), which destroyed Antony's statues and erased his name from public records—the ultimate form of character assassination and political destruction.
In summary, Octavian used the truthful content of the will to paint Antony as an unpatriotic, foreign-dominated weakling, thereby achieving the desired political harm: the destruction of Antony's reputation and the elimination of the final political rival to Octavian's absolute power.