Commodus. Not a noble character. Gibbon thought that he was more weak than evil. But perhaps it isn't very meaningful to make judgements. After all, the early life of Commodus could not have been more divorced from reality. Michael Jackson probably led a more normal life.
He showed little interest in the hard work of ruling. He happily delegated it to anyone who would leave him free to enjoy his leisure. And as a ruler of the Empire his leisure time was pretty good. He had a harem of 300 girls and 300 boys. He came to the throne young, but even so you have to at least admire his stamina.
He was also keen on sport, hunting and gladiators. He showed no interest in any of the arts. He used to have wild beasts brought to Rome from the far reaches of the Empire and beyond, so that he could kill them himself in the Circus in front of the people. This was a demeaning way for an emperor to behave. He began to style himself the Roman Hercules. This involved wearing a bearskin and carrying a club. It was a pretty ridiculous comparison. Hercules had sought out the Nemaean Lion that was strong enough to withstand arrows and fought it bare handed to save the people of Nemaea from being terrorised by it. Commodus was killing animals for fun while being well protected.
He didn't restrict himself to lions. Ostriches, elephants and rhinoceros were also displayed and then killed. Whether the Romans got much in the way of entertainment value out of these displays we won't ever know, but it does show the reach of the Empire at its height if it was able to lay hands on creatures from so far outside its borders.
But it got worse. He started dabbling in gladiatorial contests, and then started appearing in the Circus as a gladiator himself. This was behaviour definitely not consistent with the dignity of the Emperor of Rome. Gladiators could become wealthy but they were never respectable. The role he played was that of the Secutor, fighting against the Retianius. There were lots of variations of gladiatorial combat, but I think that this is the one that comes first to most people's mind. As the Secutor, Commodus would be lightly armoured and armed with a small shield and short sword. His opponent would only have a net and a trident. If he could trap the Secutor with his net and dispatch him with his trident he would live. Otherwise the Secutor at close contact would have an obvious advantage.
Needless to say. Commodus always won. Mercifully, he rarely actually killed his opponent. But he did pick up the enormous prize money. He did this 735 times which meant that the prize amounted to such a huge sum of money that it was effectlvely a tax. He also adopted the name Paulus to associate himself with the most famous and successful gladiator of the day.
The Romans must have been appalled. One senator, Claudius Pompeianus, simply refused to attend. Prominent citizens were being killed routinely by this stage so he was well aware he was taking his life in his hands by doing so, and he prudently instructed his sons to continue to show up themselves. Mind you he did have other issues. He was the senator to whom Commodus' sister Lucilla had been married - the one who had tried to kill him. He may well have decided he was due for the chop anyway. In the event, he got away with it.