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.
Dominate
Emperors imported rituals such as kneeling before the Emperor, and kissing of the hem of the Imperial robe (proskynesis). Even some Christian emperors, such as Constantine, were venerated after death. In the Eastern Roman Empire after 476 AD, the symbiotic relation between the Imperial Crown in Constantinople and the Orthodox Church led to the distinctive character of the medieval Roman state. Anastasius I was the last emperor known to be consecrated as "divus" on his death (518 AD). The title appears to have been abandoned thereafter on grounds of its spiritual impropriety. See Imperial cult (ancient Rome). The last ruler to use the titles "Dominus Noster" was Justinian I (died 565), giving place to the title of "Basileus" ("King"). In the Eastern half of the Empire, and especially from the time of Justinian I, the system of the Dominate evolved into autocratic absolutism.