Nero
After Caesar Augustus came Tiberius;
then Caligula (whose sister, Julia Agrippina, tried to kill him);
then Claudius (probably poisoned by his fourth wife, Julia Agrippina);
and then Nero (who was the son of - yes, you guessed it - Julia Agrippina).
By killing Claudius, Julia Agrippina made her 17 year-old son, Nero, the youngest ever emperor, in AD54. When Nero decided the following year that he was old enough to ignore his mother's interference in his private life, however, she switched her allegiance to his 14 year-old stepbrother, Britannicus. She wanted to try to get Britannicus recognised as emperor as soon as he became legally adult on 13 February. Strangely, Britannicus died very suddenly on 12 February. Even more strangely, it wasn't Julia Agrippina who did it. It was Nero, of course!
Statue of Nero, apparently carved by someone who admired thick necks.
Nero's relationship with his mother obviously didn't improve: in AD59, he arranged for his mother to sail on a boat which was specially designed so that it would sink. When his plan to drown her failed, because Julia Agrippina swam to the shore, he had her killed and tried to pretend she had committed suicide.
The thing that Nero is most famous for, however, is probably completely untrue. Even today, people still talk about Nero 'fiddling while Rome burned'.
In 64 AD, there was an enormous fire, known as the Great Fire of Rome, which burned for over five days. One historian who didn't like Nero wrote that Nero was singing a song, dressed up in a costume, while Rome was burning, rather than doing anything useful to stop the fire. This seems to have turned into Nero playing the lyre, which is a stringed instrument a little bit like a violin. Somehow, this then turned into him playing the fiddle, which is another word for a violin, and particularly odd since the violin wouldn't be invented for another 1500 years at least.
Other accounts are much kinder to Nero, one of them even claiming he helped to find and rescue people caught in the fire. Unfortunately for Nero, no-one remembers that. They only remember him fiddling while the city around him burned! As they say, mud sticks!