King Zarkon is the evil Drule king, father of Lotor, and enemy of the Voltron Force.
When the Drule Empire had conquered planet Arus, he demanded they hand over the royal family or 10 of the native people will die. Lora tried to convince him to stop as it was wrong, wasteful, and would only make generations rebel. So he strangled her in front of Lotor and told Lotor to dispose of her body. (Robotech/Voltron 2)