Since tyrants have had such a high profile this year, child-slayer King Herod, an important player in Matthew’s version of the Christmas story, though absent from Luke’s, is sure to bulk larger than usual in Christmas homilies.
Pompey had annexed this volatile part of the world in 64 bc, and part of the settlement involved allying with local kings. Herod’s father Antipater had been a client of Pompey and ally of Julius Caesar. Appointed procurator of Judaea, Antipater made Herod governor of Galilee, but was poisoned in 43 bc. Antony (Caesar’s successor) saw Herod as a safe pair of hands and in 40 bc, against much local opposition, made him king of Judaea and Samaria; it was only in 37 bc that Herod eventually fought his way into Jerusalem, with the help of Antony’s legions. In 31 bc Antony was defeated by Octavian (Augustus, the first Roman emperor), but Herod was kept in power and remained loyal to Rome till his death in 4 bc. He was known for his ruthlessness, maintaining a secret police and doing away with both his wife and assorted sons when he felt threatened by them. So he was certainly the sort of man who could have ordered a slaughter of innocents, though the pro-Roman Jewish historian Josephus, who had little time for him, never mentions such an act.
Ancient Greeks, who endlessly discussed the best sort of constitution, found the single ruler acceptable on condition that his powers were limited. Aristotle, for example, distinguished monarchy from tyranny on four main criteria: whether the ruler (a) was subject to the law, (b) held office for ever, or merely for a set term, (c) was elected or not, and (d) ruled willing subjects. Herod would have failed the monarch test. So would most modern counterparts.
Romans were highly sensitive on the subject.