Original sentence: The Great Dog Demon's major foe in the manga was the dragon Ryūkotsusei, whom he could not kill but sealed onto a cliff face with his claw; Myōga says this battle is ultimately the "cause" of his death and if you notice in the third movie Myoga states that he is still ingured from his battle with Ryukotsusei
Edited sentence: The Great Dog Demon's major foe in the manga was the dragon Ryūkotsusei, whom he could not kill but sealed onto a cliff face with his claw; Myōga calls this battle the "cause" of his death