Nero

Nero was the son of Agrippina the younger, who was a sister and reputed lover of Caligula (along with his two other sisters - recall Joaquin Phoenix's character in Gladiator?  Creeeeeepy.).  Through a series of wacky incidents he became emperor at 17 under the guidance of Seneca and [Sextus Afranius Burrus].

Things went well for about five years under the influence of Seneca and Burrus and then, reportedly after Nero recovered from a sickness, everything went to heck.  In 59 he orchestrated his mother's murder.  Seneca tried to argue that she was conspiring against her son (which, considering her extensive dealings in the matters of succession and her relationships with both Caligula and Claudius, is not that far-fetched) but Nero's reputation couldn't be saved. 

In 62 Burrus died and Seneca retired, and in 64 Rome burned while Nero sat on a hill playing his lyre and singing.  But then that's just rumor.  However, evidently he became increasingly fond of playing his lyre and singing, even in public - which was considered scandalous by Roman standards.  At least I'm pretty sure it went against the Mos Maiorum.  After the senate and imperial guard turned against him, Nero committed suicide, apparently lamenting his last days of artistic expression rather than the fact that he was being deposed.  Oh, well.