In the competition for worst Roman emperor ever, certain names stand out. Caligula, for example, whose debauchery and perversion are legendary to this day. Or Nero, who became renowned for his cruelty and who, by popular legend, did nothing but strum his lyre while Rome burned to ashes. Then there’s Commodus, who managed all of that and more.

Reigning from 180 to 192 A.D., Commodus all but ignored his official duties. Instead, he devoted himself to his harem of 300 females and a like number of males, played gladiator at Rome’s Colosseum and ordered the executions of countless foes, allies and family members alike. When Rome burned on his watch, he not only made little effort to stop it but insisted that the rebuilt city be renamed in his honor. He also believed himself to be the reincarnation of mythological strong man Hercules.

Little known today, but given a name-recognition boost by Joaquin Phoenix’s portrayal of him in the 2000 film Gladiator, Commodus was, in the words of Michael Kerrigan, author of A Dark History: The Roman Emperors From Julius Caesar to the Fall of Rome, “the strangest, most demented of emperors.”

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Commodus was all of 15 when his father, Marcus Aurelius, made him co-emperor and anointed him as his eventual successor, despite the fact that the young man was clearly unfit for the job. “Even from his earliest years he was base and dishonorable, and cruel and lewd, defiled of mouth, moreover, and debauched,” the early historian Aelius Lampridius wrote.

When the widely loved Marcus died in 180, Commodus became the lone emperor at age 18. Commodus was rumored to have had a hand in his death, but historians today are skeptical.

Marcus would have been a hard act to follow for any successor. Barry Strauss, professor of history and classics at Cornell University and author of Ten Caesars: Roman Emperors From Augustus to Constantine (2019), calls him “the most humane, decent and philosophical of all the emperors.” His son would be the opposite.

While Commodus enjoyed the many perks of his office, he had little interest in doing any of the work involved. Instead, he delegated that to a series of trusted lieutenants. When he stopped trusting them, he would have them murdered—often gruesomely—and appoint another one.

That, along with his immeasurable wealth, gave Commodus plenty of opportunity to pursue other passions, particularly watching gladiatorial contests and joining in them himself. “He often slew in public large numbers of men and of beasts as well,” another early historian, Dio Cassius, wrote. “For example, all alone with his own hands, he dispatched five hippopotami together with two elephants on two successive days; and he also killed rhinoceroses and a camelopard [giraffe].” On another day he killed 100 bears, spearing them from the safety of the arena’s balcony.

In one instance he assembled a large number of men who had lost their feet, dressed them up as serpents, gave them sponges to throw at him in lieu of rocks and clubbed them to death, pretending they were giants. He seems to have been more careful with actual gladiators, never killing any but slicing off the occasional ear or nose. Of course, they had the good sense to let him win their matches.

In all, Commodus reportedly claimed to have won some 12,000 contests in the arena, while also bragging that he had done it left-handed.

WATCH: Gladiators: Blood Sport on HISTORY Vault.

Sanity was never Commodus’ strong suit, and he seems to have become ever more divorced from reality as his rule went on.

Once he had persuaded himself that he was the reincarnation of Hercules, he spent enormous sums to convince the rest of Rome. Toward that end, he removed Nero's head from the Colossus of Nero, a 100-foot bronze statue that stood near the Colosseum, and replaced it with a replica of his own head; he also equipped the statue with a club and put a bronze lion at its feet to reinforce the comparison to Hercules. Other statues of him as Hercules, dressed in animal skins and brandishing a club, were dispatched to the four corners of the Roman empire.

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Commodus also decided to rename the months of the year—all of them after himself. August, for example, became Commodus, October became Herculeus, and the rest also referenced one or another of his many self-conferred titles.

When fire ravaged Rome in 191, he saw the opportunity to rename the city Colonia Lucia Annia Commodiana, or Commodus’ Colony. Romans would henceforth be called Commodiani, and the Roman Senate became the Commodian Fortunate Senate.

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Commodus’ craziness didn’t sit well with the Roman elite, although few dared challenge him publicly or lived long if they did.

He survived an assassination attempt instigated by his own sister in 182, when the would-be assassin announced his intentions before he could deploy his sword and was pounced on by guards. Commodus had him and numerous others, guilty and otherwise, murdered in retaliation. He sent his sister into exile for a brief time, then had her murdered too.

An attempted assassination in 187 also failed, but in 192, plotters fared better. Two of his high-ranking officials, possibly with the help of his mistress, first poisoned him (either with wine or beef, depending on the account). When that didn’t do the trick, they brought in a professional wrestler named Narcissus, who then strangled him.

Commodus was 31 years old.

READ MORE: Ancient Roman Emperors: A Timeline

In his 2021 book, Evil Roman Emperors: The Shocking History of Ancient Rome’s Most Wicked Rulers from Caligula to Nero and More, author Phillip Barlag awards Commodus the No. 1 spot, calling him a “self-indulgent, dim-witted oaf,” not to mention “sick, cruel, sadistic, deluded.”

Historian Strauss points out that as bad as Caligula and Nero eventually became, they each “began their reigns on high notes,” while “Commodus started out bad”—and stayed that way. In particular, his antics in the arena were an embarrassment ill-befitting his role as ruler. “If Commodus wasn’t the worst emperor in ancient Roman history,” Strauss says, “he was certainly the most undignified in the eyes of the Roman elite.”