I feel that I was physically abused as a child in a few different ways. One of them was spanking. I don't feel that spanking in general is abuse, but I'll tell you why it felt like abuse in my case. Of the three children, I was the only one who was ever spanked. I was the best behaved of the three, but was the scapegoat child. My brother, the GC, was a monster, but was never spanked, EVER. When I was spanked, it was less a punishment, and more of an event. I was made an example of. My brother and sister were called to watch. My NM always had my father carry out the spanking. Because of the nature of these spankings, I have been left with deep emotional scars. Perhaps a child who is spanked as a disciplinary measure feels differently, but I was spanked for amusement, which is a much different situation.
I was also abused by being refused medical care as a teen (the article Ann posted about daughters of Ns mentions this form of abuse). I had chronic tonsillitis starting in high school, with severe infections, excruciating pain, and high fevers. M would never take me to a doctor because she said it was my punishment for "kissing boys." I also had chronic bronchitis. My aunt, who is a doctor, believed that I was allergic to the chemicals in the science classes I was being forced to take (my so-called pre-med training). M said it was because I was smoking cigarettes, when I hadn't so much as looked at a cigarette. She finally did take me to the doctor, probably because my aunt said something, but she told the doctor I had been smoking. So I got a lecture from the doctor, not medical care. Again, I never recovered from it. That is just the ultimate act of cruelty, to deny a child medical care as a punishment, especially for something they didn't even do (and she KNEW I didn't do).
IMO physical punishment from an N is not beneficial in any way, and only scars the child, especially since in most cases, the punishment is unwarranted.