10 Doctor Who Episodes Where Evil Won
5. Mindwarp
Mindwarp has one of the bleakest endings in all of Doctor Who. In fact, Mindwarp is pretty damned bleak full stop. From the Doctor chaining Peri to the rocks to the unsettling climax in which Lord Kiv is now inhabiting Peri's mind. And then, we watch as she's killed by a furious Yrcanos.
While the ending of Mindwarp is retconned six episodes later, in the moment we all believe that Lord Kiv has succeeded in his plan. Worse still, the Valeyard and the Inquisitor both heavily imply that Peri's death was sanctioned by the Time Lords because Crozier's mind swapping experiments could not be allowed to continue!
Crucially, even when Peri is revealed to have lived, it's not because of any forgotten heroics by the Doctor. No, he still disappears in the TARDIS and leaves her to her fate, with her consciousness trapped inside the body of the aging Mentor.
So Lord Kiv briefly got his new body, and the Valeyard succeeded in making the Doctor look like the sort of man who would leave his companion to die.
That's two evil victories for the price of one.