Doctor Who: 10 Worst Things The Master Has Ever Done
5. Using Kronos To Destroy Atlantis
It's often forgotten that the mythological city of Atlantis actually exists within the Doctor Who universe... or at least it did, until the Master destroyed it.
This occurred way back in 1972, during the Third Doctor serial The Time Monster - part of which takes place in Atlantis. In this story, the Master works to gain control of a powerful creature called Kronos, and in the final episode, we see just how strong Kronos can be when it destroys Atlantis after being instructed by the Master.
Bear in mind that this was back in the early days of Doctor Who, when the production values weren't that great and the scale of the show was limited. As such, the only proper look we get of Atlantis being destroyed is a couple of pieces of rubble falling to the floor in a single room.
That being said, the Master's comment about the "ruins of Atlantis" tells you all you need to know: the entire civilisation was destroyed and many lives were lost, and all of that blood is on the Master's hands.