Arminius was a German tribal chief during the early part of the 1st Century CE, and is best known for being a total badass and giving the Roman Empire the beating of their lives.
He was born in the year 16 BCE as part of the Germanic Cherusci tribe, located East of the Rhine River on the outskirts of the Empire. The son of the tribe's war chief, Arminius was shipped off to Rome at an early age to be trained as a military commander, obtaining the rank of Equestrian and eventually leading a Roman auxiliary military force in the Balkans from 4-6 CE.
When Arminius returned from his successful campaign in the Balkans, he found that the Roman governor Varus was making a great deal of progress for the Empire by beating up on Arminius' clansmen in Germanica. Well once Arminius realized that he was totally screwed over and was actually dealing with total dicks he busted out a plan to fuck Rome's shit up once and for all. He took a brief leave of absence from the military and traveled to Germany to try and unite the tribes there for a counterattack against the Roman aggressors. The German tribes liked the idea of killing Roman bitches, so they decided to join up and stab some things with their axes and/or swords.
Meanwhile the governor of Germania, Roman general Plebius Quinctilius Varus, was about to launch a massive raid into the German lands in an effort to expand the Empire and bring glory to himself like the total cock that he was. He set out on an expedition into the Teutoberg Forest in the Fall of 9 CE accompanied by three full Roman Legions: Legio XXVII, Legio XXVIII and Legio XXIX, as well as several Cohorts of Auxiliaries and support units. Their goal was the conquest of the Eastern German tribes and the expansion of Roman rule across the Elbe river. However, as the Roman Legions broke ranks and tried to make their way through the heavily wooded forest, Arminius and his men fell upon them in an ambush and totally kicked the living shit out of them, cutting them to pieces over the course of the three-day battle.
No written record survives of exactly what happened at the Battle in the Teutoberg Forest. All that is really known for certain is that 30,000 Roman soldiers entered the woods and none returned. When Emperor Tiberius dispatched the Roman general Germanicus to the forest four years later, he learned that not only had all three legions and their auxiliaries been annihilated, but that the skulls of the fallen Roman soldiers had been nailed to the tree trunks throughout the forest to serve as a warning against future invasions. It was the single most devastating defeat of Roman forces in the history of the Empire.
Arminius didn't give a crap though; he was a badass. He was just like, "bring it bitches", and when Germanicus sent his force of 80,000 through the forest to raid German lands, Arminius once again mounted a resistance and through guerilla tactics and his cunning military strategy of "get a lot of bigass guys to run through the woods and hit the Romans with axes and broadswords", he was successful in beating back the second Roman invasion of Germany and permanently marking the border between Germanica and the Roman Empire. In fact, the division still remains today as the border between France and Germany.
Unfortunately, Arminius was another poor bastard who had bitches for in-laws. You see, his wife was supposed to marry this other dude in an arranged marriage, but after the events at the Teutoberg Forest she was so desperately turned on by how much of a badass Arminius was that she threw herself at him and they got married. This pissed off her in-laws like you wouldn't believe, and when Germanicus invaded, her father turned over his own pregnant daughter to the Romans out of spite for her actions. The Romans brought her back to their capital and it is believed that she was eventually sacrificed to Jupiter. Her son was sent off to be a gladiator and died at a young age.
Arminius was crushed by this, but didn't let it break his resolve. He continued to battle the Romans whenever they got too close to his borders, and he also successfully whipped the asses of some other German tribe that tried to seize power from him. Unfortunately Arminius was stabbed to death at age thirty-seven by members of his wife's bitchy family.
Arminius was a badass because he completely fucked up the Romans when they tried to mess with his peeps. He not only managed to preserve his peoples' independence and prevent the Romans from ever setting up rule in his homeland, but he beat their asses harder than any asses have ever been beaten. He freaking nailed their skulls to tree trunks he was so hardcore. Plus, he did it all by pulling together "barbarian" German tribes that hadn't worked together for as long as they had been in existence and he managed to make them fight as one against a common foe. He had diplomacy skills, military skills, and the ability to personally whip the ass of anyone who pissed him off (because he was a big ass German) -- all of which combined to make him a pretty serious badass.