The Romans, and to a lesser extent, the Greeks, always had one person who had the most power, a Figurehead if you will, nearly every government had this, regardless of what type of government it is.

Julius Ceaser was the Ceaser in Rome and carried much power, but he focused on conquering land so every one was okay with, except the people who killed him.

Chancellor Palpatine was the head of the old republic in it's dying decade, while traditionally the Chancellor has little direct power, Palpatine granted himself emergency powers during the war. Only to serve his own agenda

Darth Vader was the face of the Empire, and while he did wield enormous power, he was really just a pawn to the Emperor.

The Ethereals, over many years, amassed an army of different alien species from sectoids to cyberdisks, they are the ultimate leaders of the cllective, but there are hits of a higher power.

The One Earth government had many high ranking metahumans, from wonder woman to yellow lantern, but all authority was beneath the high counciler, Superman.

The Roman Empire ruled through militaristic strength, which is basically ruling through fear. Literally dozens of governmental bodies have done this, including but not limited to, The Galactic Empire, The Combine, Hydra, The Sinestro core, (literally) The One Earth government, , The Skrulls, the Agorians, Marcone’s Criminal empire, Tachyon’s Empire, Sauron’s Army, The Hutts, Certain areas of the Kree, The Kerchu, the Helghast,  the Covenant, and to an extent, The Blarg and Dreadzone. While this was mainly an excuse to write down a large number of fictional governments, they all rule through fear, like the Roman Empire. However, they don’t all do it like the romans. The Romans mainly relied and having a huge military and using that as its weapon of fear. This was also used by the Galactic Empire, Tachyon’s government, the Blarg, the Skrulls and Dreadzone. Others used Police brutality, like the One Earth government, Sinestro core and the Combine. Some used the fact that they could just make you one day ‘disappear’, namely the Hutts, and Marcone’s criminal empire. Others were just plain bloodthirsty, like the Agorians, The Kree, and Hydra.

Roman Military

The Grand army of the Empire invading Naboo

Combine Police Officer, among 'citizens'

The army of HYDRA

The Sinestro Core

The High Councilor of the One Earth Government with his two lead Enforcers

An Agorian Beast master attacking a Lombax during the Battle of Krell Canyon

One of Tachyon's Drop ships deploying Drophyd soldiers during the Invasion of Kerwan

Sauron at the head of his army

A Hutt crime lord with guards during the rise of the Hutt Cartel, Approximately 1000 years B.B.Y (before the battle of Yavin)

Ronan the Accuser, A Kree fanatic, launching an invasion on Xandar, attempting to place an infinity stone on it's surface, destroying all life on it.

A Kerchu Defender, A massive war machine built for the destruction of any outsider who have inruded on the capitol city on Jasindu.

Helghan Troops in formation.

A Covenant Elite about to kill a UNSC soldier

A Blargian warship carrying an experimental super weapon

Dreadzone's Exterminators, four undefeated warriors. From left to right, Shellshock, Eviscerator, Ace Hardlight, and Reactor

Disclaimer: I do not own these pictures and all credit goes to the respective owners.
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