Governor General Phaeton of the Neo Sapien Martian Commonwealth is the main antagonist in the animated space opera, Exosquad. Upon successfully lobbying for the Exofleet (a kind of U.N. defense force, circa 2120) to run off to Saturn and battle Space Pirates, Phaeton ordered his fleet to launch a surprise attack on Earth and Venus. The subsequent conquering and enslavement of humankind lasts until Phaeton's defeat during the series finale.
Phaeton, like most other Neo Sapiens, was born in a massive breeding complex on Mars. Fifty years prior to where the show starts off, he was part of a large Neo uprising on Mars. The rebellion was crushed, and Phaeton went on to eventually become leader of the Neo Sapien "government". However, he maintained fanatic hatred for terrans, and secretly transferred funds to amass an invasion fleet capable of conquering the Homeworlds (Earth and Venus). When some terran officials were calling for war against the Pirates, Phaeton saw his opportunity and seized it.
With most tyrants, real or fictional, there are going to be comparisons with Adolf Hitler. Phaeton is no different. Quite a few Hitler/Phaeton comparisons go well beyond the simplistic "he conquered stuff", "he was mean and started a war", or "the good guys beat his sorry ass."
Phaeton used his people's anguish and torment to his advantage. He rallied them behind a the notion that a previous humiliating defeat must be avenged. Phaeton often would not trust the judgment of his military advisors (who actually knew what they were doing), and instead used his visions of "destiny" to guide him. Halfway through the series, Phaeton contracts "AutoMutation Syndrome". This condition has no cure, causes Phaeton to become physically deformed, and has hugely adverse effects on his sanity. (Can you say syphilis?) During the final episodes, crippled by his debilitating disease, Phaeton refuses to leave his underground bunker beneath his capital city.
Phaeton also makes a huge blunder in allowing the Pirates to eventually ally with the Exofleet instead of with him. The Pirates' large numbers and cutthroat tenacity are invaluable to the Exofleet in their war against Phaeton. (Can you say Soviet Union?)
Oh, and the series itself has a number of allusions to the Nazis. For instance, in one poignant scene, a Neo Sapien commander informs a group of human laborers that if they don't cooperate that there is a "final solution to the human problem." The episode in which Phaeton launches his invasion of the Homeworlds is entitled "Blitzkrieg." And on more than one occasion during the series, someone says something to the effect of "it's not the Neo Sapiens we're fighting, it's Phaeton's tyranny." This corresponds to how it wasn't the German people that were the problem, but Hitler and his cronies. Also, Neo scientists were creating devastating genetic warriors in the war's waning days, but not enough were created to have much of an effect on the outcome. (Which reminds me of the Luftwaffe jets.)
Speaking of cronies, Phaeton bestows power and responsibility on his three greatest generals: Typhonus, Shiva, and Draconis. Besides being three of the coolest American animated characters of all time, each general is assigned a specific task during the invasion and occupation.
Typhonus is Phaeton's battle minister and personal emissary. He usually remains on Mars at Phaeton's Martian Palace. Draconis, while not secretly plotting Phaeton's assassination, heads up the Venus occupation. Shiva, the most effective and loyal of the three, has the most demanding position of leading Earth occupation.
Incidentally, I would like to mention I'm a big fan of animated shows involving space battles, mechs, shitloads of historical/religious allusion, or all three. (This is why I love Evangelion and Cowboy Bebop.) Exosquad is unique because it's an American show that can stand up to its Japanese counterparts (though, not musically, of course.)