Doctor Who: 8 Times The Doctor Has Killed
3. He Poisoned Doctor Solon
It's no secret that the Doctor possesses an immense amount of brainpower. He's so smart that he could probably build the most devastating bomb in the universe in just one weekend, or create a deadly plague that wipes out entire populations.
Thankfully, he's got two kind hearts so his intentions are mostly pure, but he has displayed the lethal capabilities of his genius intellect in the past. Case in point: that time he managed to create a deadly poisonous gas - while imprisoned - and use it to kill Doctor Solon.
In the Fourth Doctor story The Brain Of Morbius, the Doctor and Sarah Jane Smith end up clashing with Doctor Solon, who is attempting to create a new body to house the brain of Morbius, a sinister Time Lord. Towards the end, Solon seals the Doctor and his companion away, getting them out of his (terrible) hair so he can continue his work on Morbius uninterrupted.
But, as ever, you should never count the Doctor out, even when he's trapped with limited resources. In this instance, he manages to craft some poisonous gas, pump it through a vent, and kill Solon in an attempt to stop Morbius from rising.
Okay, yes, this was a tricky situation, but at the same time, couldn't he have just built some knockout gas or something?