Chaktra

The Chakra were a war-like race who were engaged in multiple conflicts throughout the galaxy.

One day, they came to the Telphin homeworld and, thanks to a garbled report, took them to be allies of their enemies. They then proceeded to bombard the planet, killing all the Telphin in a single day.

The Seventh Doctor would later recount this story to Simon Galway to prove that war was unjustifiable. (DWM: Memorial)