In Ancient Greece a Tyrant wasn't "a cruel an oppressive ruler". A tyrant was someone who illegally seized power, usually from a cruel and oppressive ruler and with the support of the oppressed.
Conversely: in Ancient Rome a Dictator was someone who was legally granted absolute power for six months by the Senate to deal with a crisis.
FYI Injustice doesn't take place in Ancient Rome or Greece.
Though that could explain Wonder Woman being a hateful bitch in the series.