Markhan Genocide

The Markhan Genocide, was, according to the Seventh Doctor, one of the Daleks' greatest atrocities. In it, the Daleks released a plague on the planet Markhan as a prelude to invasion, wiping the natives out. In an alternate timeline where the Daleks were peaceful, Markhan's inhabitants were still alive 200 years later. (PROSE: The Ripple Effect)