Exactly the problem. Like she just appeared and killed him. I understand he is hated but it isnt going to change the fact that it feels like mehish move.
Yeah, I agree with this. The mother being the one to kill him is a perfect ending for a sexist asshole like Naoya, but the delivery kind of sucks. Her motivations are ok, any woman in the Zenin clan probably would approve of killing this little prick. But... How the hell does the (badly injured) mother make it conveniently to the place where Naoya is to stab him?
Eh, I guess we'll always have fanfics or our imagination to flesh some things if needed, but it seems like a bit of a waste in the delivery