User blog comment:Gary299/High School DxD BorN episode 4 review/@comment-3965848-20150425180921/@comment-26209278-20150425182953

Well, remember it was still a Dragon King clone. Even if Issei used Ascalon on it, it wouldn't be a one hit finisher....

He doesn't use the actual Ascalon much in the LN, he usually transfers it's power into his fist (more so when the Evil dragons appear)