Well, Nine is the only (nu) Doctor offhand I can think of who balked at killing people -- 10 wiped out the Rancoss and waved his hands and looked megalomaniac while he did it and he's allowed companions/events and circumstances to kill quite a few folks, as have many of the old Doctors as well.

Dr. Who isn't actually as light, fluffy and gentle as people seem to think and Eleven has made it clear from the beginning that pissing him off results in Very Bad Things.