It's been a while since I played DMC2 last time, but since I improved my skill in DMC series overall I decided to try it again. Nefasturris isn't hard boss and I may redo this on DMD difficulty. I've redone this fight on hard difficulty. Compared to normal, it's much more intense and harder. When you destroy his body he will cast his magic crazy fast and you have to kill him quickly to not let him cast some really hard to avoid magic patterns. I still try to do this on DMD, but this even more crazy because those patterns cannot be avoided due to his increased health and they have to be dodged instead, which is almost impossible. I guess this game wasn't made for no damage runs.