In Doctor Who Episode 2 of Series 7, Dinosaurs in a Spaceship, the Doctor chooses to leave Solomon on the spaceship which is about to be destroyed, allowing him to die.
The obvious alternative would be to send the spaceship out unmanned, for example, or the inclusion of an explanatory line stating that the spaceship would not be able to fly unmanned. It is very rare for the doctor to kill anyone directly, and even rarer for him to do so when it wasn't strictly necessary for the survival of his companions and himself.
Previously in Dr Who, Davros suggests that the doctor is evil at heart, manipulating companions to die or kill for him, because he is afraid to do so himself. This episode contains not only an example of a companion sacrificing herself (Nefertiti in this case), but also the doctor choosing to let someone die.
Is this not unusual behaviour for the Doctor? Or has he always let those he deemed 'evil' die?