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.
Roman expansion in Italy
The last king of Rome, Tarquinius Superbus, is portrayed by the sources as a powerful, but tyrannical, king. He is said to have taken Pometia by storm and Gabii by ruse, colonized Signia and Circeii, and to have organized the Latin states into an alliance under his own leadership. However Tarquinius was deposed by a conspiracy led by two of his relatives, Lucius Junius Brutus and Lucius Tarquinius Collatinus. These two then founded the Roman Republic with themselves as its first two consuls; traditionally the overthrow of the monarchy has been dated to 509 BC. Tarquinius is supposed to have sought refuge with king Lars Porsenna of Clusium, who marched against Rome to reinstate the king. After various heroic acts by brave defenders of Rome, Porsenna gave up and instead attacked Aricia, but was defeated by an alliance of Latin cities and the Greek colony of Cumae. Modern historians have had difficulties accepting this tale and have instead proposed that Porsenna actually captured Rome and deposed Tarquinius and replaced him with two leading aristocrats. With leadership of the city divided, Rome would have been easier for Porsenna to control.