Doctor Who: 8 Times The Doctor Has Killed
2. He Blew Up An Entire Legion Of Cyber-Ships
There's some argument as to whether or not killing a Cyberman counts as taking a life, since they're mostly just emotionless voids that are fuelled by one sole desire: to delete their enemies.
Then again, they have proven capable of possessing a bit more humanity (like when Cyberman Danny Pink was able to have a tearful goodbye with Clara), albeit under exceptional circumstances. So we can't really say whether or not their lives should be given less value than your average warrior from any other race.
Even if you are of the mindset that they all deserve to die, the Doctor's explosive antics at the start of A Good Man Goes To War still feel like a bit much.
The opening few minutes of the episode find the Doctor and Rory attempting to track down the recently-kidnapped Amy Pond. To do this, Rory boards a Cyber-ship and questions them about her location, informing them that he has a message from the Doctor to boot. When the Cybermen ask what this message is, the entire fleet of ships in the sky behind Rory explodes in a massive ball of flame.
To be clear, that's thousands of Cybermen all gone in an instant, and all because the Doctor wanted to gather some information. The Time Lord has eliminated Cybermen before, true, but never on this scale, and never with such disregard for their lives.
He couldn't have found out Amy's location some other way? Been a bit stealthier? Was blowing thousands of Cybermen to hell really the only option here? It was a badass visual at least, so there's that.