Correctamundo! Genesis of the Daleks, from the 4th Doctor's first series in 1975. Afterwards he was in every TV Dalek story to the end, although only appearing as himself briefly at the end of 1988's Remembrance of the Daleks.
The Dalek Empire was portrayed as much more powerful, generally speaking, in the 1960s but by the 1970s-80s they were more vulnearable, always needing Davros, having civil wars with various factions, and only once on screen did we even see an Emperor. That was in 1967's Evil of the Daleks, but I don't believe it was the same Emperor seen later.