Nero is one of the more famous Roman Emperors. He started out as a pretty good emperor. But he was ill. It affected his mind. Nero wasn't insane when he became emperor. He slowly became insane while he was emperor.
Over time, Nero became murderously insane. He had hundreds of people killed for no reason other then they caught his eye. He even ordered some leaders of the Roman Senate to kill themselves. This drove the Senate to action. They tried to arrest Nero, which was amazing really as they did not have the power to do that. Nero was the emperor. He was a dictator. He had total power. But, when Nero found out people were coming for him, he committed suicide.