The Great Migration in Europe eventually proved fatal to the Western Roman Empire, but the first casualties were the Thervingi Goths.
Julian the Apostate was the last pagan emperor of Rome, who was the last emperor to try and end Christianity - but the game was up.
Ridley Scott's epic Gladiator (2000) throws history to the wind, and is only concerned with one question: "ARE YOU NOT ENTERTAINED?!"
Diocletian’s reforms ending Rome’s Crisis of the Third Century are greatest in how he changed Rome’s military, and new army of bureaucrats.
Diocletian set out not to merely end Rome's third century crisis, his reforms aimed to recreate the Roman Empire into his idealized vision.