Who was the emperor of Rome after Diocletian?

Nero is Overthrown by Galba Roman Governor, Nero Commits suicide ending of the Julio-Claudia Dynasty. Gala does not stay on the throne for long, he gets overthrown and replaced by Otho. Otho is overthrown and replaced by Vitallius. Vitallius also get overthrown and is replaced by Vespasian who is considered a "good Emperor." Galba, Otho, Vitallius and Vespasian rain is known as; "Year of 4 Emperors." (69 CE/AD)