Vengeance of Varos Sixth Doctor. For some reasons there is a controversy about this episode. I rewatched it to see what the big deal was. I couldn't find anything disagreeable.
Well it was the 80s, and a Children's show, so, it's a pretty grim concept. Plus some people get bent about the acid pool thing, with The Doctor "pushing" the guy in.
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?