Tiberius

Tiberius was an Emperor of Rome for a short period between Augustus and Caligula. He was murdered by his Caligula alongside many of Caligula's family members. A fact that alarmed the archangel Michael.

Given Xena's statements about "run-of-the-mill" Roman Emperors, it's likely that Tiberius was also "a psycho, a sex addict, and a murderer."