What development most directly worsened relations between Antony and Octavian in the years before Actium?

Explanation

Antony's personal and political alliance with Cleopatra, culminating in his distributing eastern lands and titles to her children, alarmed Roman opinion and gave Octavian a propaganda weapon against him. Octavian's marriage to Octavia had actually been arranged to smooth relations between the two men, and Antony's military activity and Lepidus's earlier position in Africa were not the direct trigger of the late breakdown.