Doctor Who: 10 Worst Things The Twelfth Doctor Ever Did
8. Using O'Donnell As Bait In Before The Flood
In the two-part Under the Lake and Before the Flood, the Doctor and Clara land on an underwater base where the crew are being attacked by what appears to be ghosts. One of these crew members is Alice O'Donnell, a systems technician who is also a fan of the Doctor.
The Doctor decides to travel back in time to figure out what caused the ghosts, taking O'Donnell and another crew member with him. After they leave a ghost of the Doctor appears in the base and he's repeating a list of all the characters' names.
The Doctor manages to deduce that this list is likely the order that they're going to die - and O'Donnell is next.
Upon realising this the Doctor decides not to inform O'Donnell of her impending fate, something that leads to her dying moments later. Even Bennett, a close friend of O'Donnell, states that it was as if the Doctor wanted to test his theory, which the Doctor doesn't deny.
While she may have still died even if she knew her life was in danger, as it stands the Doctor took no direct action to protect her and all for the sake is seeing if he was correct.