Ryuukotsusei

InuYasha's father first fought him in the older days and sealed him away with one of his claws. He has an incredible armored hide that is nearly impenetrable. His power level is also so high that when he fired a blast from his mouth, Miroku's wind tunnel was unable to absorb the attack and only slightly changed its trajectory away from InuYasha.

Ryuukotsusei is ruthless and has a mask that exists on his forehead through which he speaks. His attack is Raigekidan (Thunder Attack Bullet), which is the form of a giant white ball of explosive energy, which he emits from his dragon mouth instead of fire, and could easily have defeated InuYasha with a final blow if InuYasha wasn't able to learn and use the Bakuryuuha just in time to defeat the dragon. Myouga's protests reveal that it was Ryuukotsusei who inflicted the severe injuries on InuYasha's father that were the main cause of his death shortly after sealing Ryuukotsusei away.