Roman emperor
The Western Roman Empire collapsed in the late 5th century. Romulus Augustulus is often considered to be the last emperor of the West after his forced abdication in 476, although Julius Nepos maintained a claim recognized by the Eastern Empire to the title until his death in 480. Following Nepos' death, the Eastern Emperor Zeno abolished the division of the position and proclaimed himself as the sole Emperor of a reunited Roman Empire. The Eastern imperial lineage continued to rule from Constantinople ("New Rome"); they continued to style themselves as Emperor of the Romans (later βασιλεύς Ῥωμαίων in Greek), but are often referred to in modern scholarship as Byzantine emperors. Constantine XI Palaiologos was the last Roman emperor in Constantinople, dying in the Fall of Constantinople to the Ottomans in 1453.
Final War of the Roman Republic
Cleopatra did not immediately follow Antony in suicide. Instead, in a last-ditch effort, Cleopatra opened negotiations with Octavian. Cleopatra begged Octavian to spare Caesarion’s life in exchange for willing imprisonment. Octavian refused. Within a week, Octavian informed Cleopatra that she was to play a role in Octavian's Triumph back in Rome. This role was "carefully explained to her", while Caesarion was "butchered without compunction". Octavian supposedly said "two Caesars are one too many" as he ordered Caesarion's death. According to Strabo who was alive at the time of the event, Cleopatra died from a self-induced bite from a venomous snake, or from applying a poisonous ointment to herself. Learning of Cleopatra's death, Octavian had mixed feelings. He admired the bravery of Cleopatra, and gave her and Antony a public military funeral in Rome. As they left Alexandria, a new age dawned when Rome annexed Egypt. With Cleopatra's death, the final war of the Republic was over.
Within a month, Octavian was named Pharaoh, and Egypt became his personal possession. By executing Antony's supporters, Octavian finally brought a century of civil war to a close. In 27 BC Octavian was named Augustus by the Senate and given unprecedented powers. Octavian, now Augustus, transformed the Republic into the Roman Empire, ruling it as the first Roman emperor.