Drenz

Drenz was the pacifist ruler of the humanoid Daleks. He demanded that Minister Zolfian stop his plans to wage war against the Thals, warning that they could destroy Skaro. Zolfian instead shot and killed him, declaring that Drenz was unfit to rule the Daleks. (TV21: Genesis of Evil)

Later accounts would claim this occured in 2003 and that after this event Daleks abandoned personal names. (DWA: The Dalek Dictionary)