The entire Galran Empire watched as the Altean home-world burned only to watch it explode moments later. Vengeance freshly attained after dictator Emperor Zarkon and his witch and skilled warrior wife, Empress Elara slaughtered the Altean royal family, showing no mercy.
Mercy is something they didn't care for. Not anymore. Blinded by quintessence, they wanted more, they wanted total control of the universe. They'd have it at any cost.
Elara, once a kind, intelligent, gentle, radiant soul, is now an evil, clever, merciless killer loyal to her husband. Her looks weren't altered much but her once shining golden eyes are now bright glowing purple, her bright purple fur, now duller, same for her hair.
Emperor Zarkon, was always intimidating but now, he's a menacing beast of vengeance. He, just like Elara, is devoted and loyal to her only. Neither of them take orders from anyone but each other, well, Elara does as her husband asks but she does have a say in his orders.
The reason for the Galran Empire's sudden outburst of violence was because of something very tragic that happened to Zarkon and Elara. It was personal. It was something they'd never forget. Something they would be haunted by forever. Nobody would ever understand what they've suffered.
All the millions of inferior living beings knew was that they'd be in for a lot of torture.