Davros

An Emperor Dalek was usurped by Davros, who refered to him as "the upstart". (COMIC: Nemesis of the Daleks, Emperor of the Daleks!)

The Death Wheel
In the 26th century, the Emperor personally attended the construction of the Death Wheel in orbit of the planet Hell. Demanding to know why Helkogen production had dropped, the Emperor was answered by an Ogron, who reported that the Helkan slaves were working as fast as they were able but required food and rest. Enraged, the Emperor exterminated the Ogron and ordered the routine extermination of the Helkans until production increased, deeming completion of the Death Wheel imperative for Operation Genocide.

Soon after, a cargo ship carrying intruders to the Death Wheel was intercepted. The Seventh Doctor and Kemlo, a Helkan, were presented to the Emperor aboard the Death Wheel. The Emperor recognised the first seven incarnations of the Doctor as an enemy of the Daleks. Subjecting the Doctor to interrogation with his Imperial Guard Daleks, the Emperor revealed his intention to cleanse the planet of Hell of "humanoid infestation". The Emperor was confused to be addressed by the Doctor as Davros, a name which he did not recognise, with the Doctor soon realising his mistake. Alerted to another humanoid intruder, the Emperor order his Imperial Guards to exterminate the Doctor. However, the Doctor was rescued by Dalek Killer Abslom Daak, who killed the Imperial Guards before making off and freeing the Helkan slaves with the Daleks in pursuit. Ultimately, Daak, after ensuring the Doctor and the Helkans got to safety, destroyed the Death Wheel, seemingly at the cost of his own life. (COMIC: Nemesis of the Daleks)

Behind the scenes

 * The design of the Dalek Emperor's casing was a combination of Davros' Imperial Emperor casing from Remembrance of the Daleks and the Golden Emperor from The Dalek Chronicles.