What kind of demon is Akura-ou?
Akura-ou is an oni, a Japanese youkai that is known for having horns growing on their head, being physically big and strong, and having a wicked personality.

Oni have been used as villains ever since Japanese folklores like Momotaro, which introduces Red Oni and Blue Oni as the main antagonists.

Other characters that are based on oni (warning: TV Tropes):


Dragon Ball - King Enma
Smile Pretty Cure! - Akaoni
Yaiba - Onimaru