Doctor Who: 10 Times The Doctor Gave Zero F*cks About His Companions
2. Forcing Bill To Play Nice With Missy
The Doctor has made many mistakes throughout NuWho, but trusting Missy to keep his companions safe was one of the biggest errors he's ever made.
Desperate for his fellow Time Lord to show her good side, the Doctor sets Missy up with a "test": he will choose a distress signal at random, and send Missy, Bill, and Nardole out to assess - and hopefully improve - whatever situation they find.
Sounds like a decent idea on paper, but not everyone is onboard. Specifically, Bill strongly protests: she tells the Doctor that Missy scares her, that she's a murderer, and that this whole thing is a bad idea. And in the end... she's bang on the money.
While out on a mission, Missy fails to calm down an angry and agitated member of a colony ship, which results in him blasting a massive hole right through Bill's chest.
The Doctor ignored Bill's protests and used her as a part of his scheme, prioritising Missy's heroic turn over the safety of his companions. And where did this lead? It led to Bill getting horribly murdered, and later, grotesquely transformed into a Cyberman.