Augustus - Established the imperial cult
The first true Emperor of Rome, Augustus claimed power after a vicious civil war that erupted in the wake of Julius Caesar's death.
Although Augustus is widely considered one of Rome's greatest rulers, his decision to fashion himself as an all-powerful emperor paved the way for the unrestrained cruelty of his successors.
Claudius II - Punched a horse
An astute tactician who achieved several notable victories against the Visigoths, Claudius II appears, for the most part, to have been a fairly benevolent ruler.
Claudius was also a man of immense physical strength, which he apparently once demonstrated by punching the teeth out of a horse's mouth.
Constantius Chlorus - Destroyed churches
In the grand scheme of things, Constantius Chlorus was pretty relaxed in his attitude towards Christians, by which we mean he didn't feed any to the lions.
That's not to suggest that he was particularly tolerant, however, as hundreds of churches are known to have been destroyed on his orders.
Marcus Aurelius - Persecuted minorities
Often referred to as Rome's "philosopher Emperor," Marcus Aurelius was deeply thoughtful, and his diary is still considered one of the most important treatises on Stoicism.
Although he strove to improve the lives of most Roman citizens, Aurelius also mercilessly persecuted Christians and other minority groups.
Aurelian - Turned emperors into god-like figures
Before the reign of Aurelian, Roman rulers were typically viewed as soldier-emperors. However, after ushering Rome through a particularly perilous period, Aurelian decided he deserved to be viewed as a god.
This idea that emperors were borderline deities was used by many of Aurelian's successors to justify their rampant cruelty.
Tiberius - Handed control to Sejanus
Rome's second emperor, Tiberius quickly tired of ruling, and he handed control of the empire to the Praetorian Prefect Sejanus.
Sejanus proved to be a brutal and merciless ruler, but Tiberius did nothing to rein him in, instead moving to the island of Capri to live a life of undisturbed luxury.
Diocletian - Persecuted Christians
By the time Diocletian claimed the Roman throne in 284, the empire had been left in disarray by decades of bad leadership.
Diocletian used his absolute power to implement reforms that restored Rome's former glory, but he also enacted a vicious and protracted campaign of persecution against Christians.
Honorius - Brought about the sack of Rome
Although he wasn't as vindictive as some of Rome's emperors, Honorius' incompetence and weak resolve set the empire on a path of ruin.
Honorious' lack of strategic ability resulted in a string of military defeats that culminated with the sacking of Rome by hordes of Visigoths.
Galba - Confiscated the property of Roman citizens
The first Roman Emperor after the fall of Nero, Galba was 71 years old and in poor health by the time he took the throne.
Galba tried to rebuild Rome's finances by confiscating the property of its citizens, which went down predictably badly. After only six months in power, the emperor was assassinated by his successor.
Carinus - Seduced his tribune's wife
Although there aren't many reliable records of Carinus' rule, the writings that do exist tend to characterize him as one of Rome's worst emperors.
Carinus apparently used his position to seduce the wife of one of his tribune's, although it proved to be his undoing when said tribune murdered him in retaliation.
Julian - Persecuted Christians
Julian was the last non-Christian emperor of Rome, and he was greatly concerned with promoting traditional Roman religious beliefs.
In an effort to clamp down on Christianity, Julian passed legislation banning its adherents from teaching, although he was more tolerant than many of his predecessors.
Otho - Betrayed Galba
Although Otho was initially a close confidante of Nero, the pair had a falling out after the Mad Emperor seduced his wife.
Otho later allied himself with Galba to help overthrow Nero, but he then betrayed and assassinated Galba so that he could claim the throne for himself.
Justinian - Indiscriminately crushed the Nika uprising
Although Justinian was an effective ruler, his policy of enacting heavy taxes to fund the wars he launched made him deeply unpopular with the Roman populace.
The Nika uprising of 532 CE was a direct response to Justinian's autocratic rule, and he responded by indiscriminately killing anyone who might have been involved.
Carus - Executed classmates he didn't like
Petty and spiteful in equal measure, Carinus used the power that came with being Roman Emperor to avenge a long list of perceived grievances.
Although he committed plenty of atrocities, his worst act was ordering the executions of any of his classmates who'd ever mocked him.
Trebonianus Gallus - Betrayed Emperor Decius
The reign of Trebonianus Gallus is widely considered one of the worst periods in Roman history, with the Empire ravaged by plagues, invasions and internecine strife.
Gallus' worst offense actually took place before he became emperor, when he betrayed his predecessor - Emperor Decius - setting him up to be killed by the Visigoths so he could claim the throne.
Maximinus Thrax - Excessively funded the military at the expense of regular citizens
While he was an astute military tactician, Maximinus Thrax was mostly disinterested in domestic policy. As a result, the emperor spent the majority of his reign waging a series of pointless and costly wars.
Thrax also had little respect for anyone who wasn't a soldier, so he was unsympathetic to the plight of his increasingly poverty-stricken subjects.
Maxentius - Seized property from Christians
Like the majority of Rome's early emperors, Maxentius followed a polytheistic religion, and he viewed Christianity as heretical.
Although Maxentius ended some of the bloodier policies of persecution that his predecessors had enacted, the emperor still ordered the large-scale confiscation of property that belonged to Christians.
Severus Alexander - Spent too much money on the military
Severus Alexander's approach to government was succinctly summarized in his dying advice to his son: "Enrich the soldiers, and scorn all other men."
Severus protected his power by spending vast sums on the military, which kept the soldiers on side and prevented a coup but also exacerbated poverty throughout the empire.
Trajan - Invaded Dacia
For the most part, Trajan's reign is seen as one of the more prosperous periods in Roman history. That said, he still made a few crucial blunders.
The worst was conquering the kingdom of Dacia, which afforded Trajan a minor victory but also removed the buffer between Rome and the barbarians, which would eventually have calamitous consequences.
Hadrian - Persecuted Jews
One of Rome's most accomplished emperors, Hadrian significantly strengthened the empire during his reign, famously building an enormous wall across Scotland to keep out barbarians.
However, like many of Rome's emperors, Hadrian was responsible for some ugly campaigns of persecution, in this case targeting Jews.
Claudius I - Invaded Britain
For centuries, Roman emperors had fantasized about conquering Britain and claiming its precious resources, which included gold, iron and cattle.
The first emperor to actually launch an invasion was Claudius I. While the campaign was ultimately successful, it led to some of the most brutal fighting in the history of the Roman Empire.
Elagabalus - Defiled a Vestal Virgin
Elagabalus' short but turbulent reign serves as proof that handing limitless power to a 14-year-old probably isn't the wisest of ideas.
The teenage emperor was infamous for his sexual appetites. While most records avoid going into too much detail about Elagabalus' proclivities, one document reports that he "defiled a Vestal Virgin."
Constantine the Great - Boiled his wife alive
An effective ruler he may have been, but Constantine the Great had a capacity for cruelty that matched even Caligula's.
Even those closest to Constantine weren't safe; the emperor executed both his son and wife, the latter of whom was boiled alive.
Andronikos I - Had his political enemies blinded
During his reign, Andronikos I was often referred to by the nickname "Misophaes," which translates to "hater of sunlight."
This nickname had nothing to do with an aversion to going outside, but was the result of Andronikos' habit of having his political enemies blinded.
Magnus Maximus - Betrayed the previous emperor
A general in the Roman army during the reign of Gratian, Magnus Maximus became incredibly popular as a result of his successful conquests in Britain.
The popularity eventually went to Maximus' head and he turned on Gratian, capturing the emperor after vanquishing his forces and slaughtering him in cold blood.
Pupienus - Allowed the assassination of Balbinus
In 238, Pupienus caught wind of a plot to assassinate the popular Balbinus, with whom he was sharing the emperorship. Pupienus decided against warning Balbinus, planning to take the throne himself.
What Pupienus missed, however, was that he was also one of the targets, and he was assassinated shortly after Balbinus.
Julian II - Launched a pointless war with Persia
Julian II was a massive fan of Alexander the Great, and he wanted to replicate the Macedonian generals military accomplishments.
To this end, Julian launched a completely unnecessary war with Persia that weakened Rome, made its citizens poorer and needlessly wasted countless lives on the battlefield.
Theodosius - Left the empire to his son
For the most part, Roman emperors carefully chose their successors, often selecting generals who had proved themselves worthy of the role.
Theodosius I broke with this tradition, instead leaving the empire to his son Honorius, who - as we've already covered - was largely responsible for the collapse of the Roman Empire.
Valens - Brutally executed anyone he felt threatened by
The reign of Valens was mostly unremarkable, with the emperor taking an even, carefully considered approach to the decrees he made.
However, Valens also suffered from the paranoia that afflicted many emperors, and he was known for executing anyone he felt suspicious of in the most vicious ways possible.
Septimius Severus - Executed innocent senators
Although the emperor was the most powerful figure in Rome, the senate still wielded plenty of power of its own.
This bothered Septimius Severus, so he had any senator that interfered with his plans arrested, falsely charged with treason and summarily executed.
Commodus - Killed hundreds of lions for fun
Commodus was the son of Marcus Aurelius, but the apple couldn't have fallen further from the tree. While Aurelius was benevolent, disciplined and wise, Commodus was vindictive, capricious and cruel.
Commodus enjoyed getting his hands dirty in the Colosseum, although he ensured the fights were never fair, and he was particularly fond of slaughtering lions.
Vitellius - Forced his mother to starve herself to death
Within a matter of months after becoming Roman Emperor, Vitellius brought the empire close to financial ruin with his habit of throwing hugely extravagant feasts and parades.
Vitellius also forced his mother to starve herself to death, due to a prophecy that he would rule longer if she died.
Probus - Wiped out the nation of Lugii
During his six-year reign, Probus' habit of showing restraint when quelling rebellions led to his reputation as one of Rome's most merciful rulers.
However, there are plenty of incidents that suggest he may not have really deserved this reputation, such as the time he exterminated the entire nation of Lugii.
Caracalla - Murdered his brother in front of their mother
For all its perks, ruling the Roman Empire was a pretty dangerous job, and many emperors were known for being paranoid. Caracalla was no exception.
The young emperor executed anyone he felt threatened by, including his own brother, whom he had murdered in front of their mother.
Vespasian - Built the Colosseum
Although it's now regarded as one of the world's most astonishing pieces of architecture, during antiquity the Colosseum's blood-soaked sands represented the cruelty and bloodlust that was rife in Roman culture.
The giant amphitheater was built on the orders of Vespasian, and he always intended it to be used as a venue for horrifically violent entertainment.
Caligula - Beat a priest to death with a mallet
A strong contender for the title of Rome's worst emperor, Caligula was far more interested in indulging his bottomless appetite for sadism than he was with actually ruling.
It's hard to pick one example that best encapsulates Caligula's cruelty, but one of the more infamous incidents involved him beating a priest to death with a mallet while gleefully laughing.
Domitian - Executed his own niece after getting her pregnant
Domitian ascended to the throne after the death of his older brother Titus, and no one was safe from his paranoia.
The emperor's most despicable act came when he had his own niece executed on trumped up treason charges, shortly after he got her pregnant.
Antoninus Pius - Crushed the British
Although Rome successfully conquered Britain, the island's populace continued to wage guerrilla warfare against the occupying troops, often with devastating results.
This was finally ended by Antoninus Pius, who crushed British resistance by instructing his forces to mercilessly slaughter entire towns and villages.
Constantine II - Murdered his male relatives
After the death of Constantine the Great, his son - Constantine II - asserted his right to claim the throne as Roman Emperor.
Constantine was deeply insecure of his power, so to ensure he faced no threats he ordered the murders of most of his male relatives, many of whom were still babies.
Nero - Had his own mother murdered
It didn't take long for Nero to earn the nickname "the Mad Emperor," and he certainly lived up to the moniker.
Although Nero committed multiple acts of unspeakable evil throughout his reign, arguably his most heinous moment was having his own mother murdered for opposing his affair with Poppaea Sabina.