Bonnie

Bonnie was the Zygon leader of Truth or Consequences, a radical group of young Zygons who opposed Operation Double, feeling that Zygons should be free to show who they really were, instead of being forced to hide as humans. Taking the form of the Doctor's companion Clara Oswald, Bonnie worked to sabotage the Twelfth Doctor, trying to lead him into various death traps, but failed at her task. Eventually, during a stand-off with Kate Stewart with the Osgood Boxes, the Doctor managed to help Bonnie see that nothing could come from her "winning", other than a senseless cycle of violence, in which she'd lose to the next violent uprising. Instead, her new role could be protecting others. Taking this new purpose to heart, Bonnie decided to take the vacant spot left by the Osgood killed by Missy. From this point onwards, she was known as Petronella Osgood. Both promised the Doctor they would reveal which of the Osgoods Missy had killed, but only when it would no longer matter whether the remaining Osgood was human or Zygon.