Kraarn

According to Zargath, Kraarn of the Kraagaaron was one of the most evil beings in Mutter's Spiral and had laid waste to whole solar systems and enslaved entire species.

He had been defeated by the Doctor, and intended to ally with other aliens at Research Base Truro to eliminate him. While outlining his strategy, he involuntarily caused an electrical surge, which killed him on the spot. (COMIC: Death to the Doctor!)