Uther Pendragon (The Steampunk Adventures of Sorcerer's Apprentices)

Uther Pendragon is the posthumous main antagonists of the first part of The Steampunk Adventures of Sorcerer's Apprentices. He was a ruler of Camelot whom, after his wife Igraine killed by Vortigern, an evil sorcerer and former ruler of Camelot during their attempt to smuggle the baby Arthur to a group of people whom later revealed as forerunners of Merlineans, he turned into a ruthless tyrant whom persecuted magic and everything that related with it. His extreme methods in persecuting magic even goes so far to genocidal level, as he responsible for wyverns' extinction and nearly wiped out the dragons had they not smuggled their eggs somewhere beyond the tyrant's reach.

His hatred of magic and severe punishment of those who used it ultimately caused Morgana whom to turn against both him and Merlineans, and the King's death sparks Albion Great War.

Personality
Through the fan-fiction narrations and being referenced several times (particulary by Corinth), his wife's death led him into indiscriminate vengeful grief on anyone or anything that related with magic. His said grudge appeared to led him became a ruthless tyrant whom largely bereft of positive traits or remorse toward magic users and magical beings. He even personally killed Elena, a wyvern whom known being Corinth's wyvern wife in cold blood that enciting the dragons' wrath.

The king's negative traits of course, would be his downfall. Corinth even stated that even if he won't be the tyrant's downfall, someone else would, which turned out to be true: Morgana and Zacros eventually became the king's killer.