depends on which part of the neck you’re punching and how powerful the punch it. Also, there are ways to better take punches by cushioning the hit through effective breathing techniques and body movements. So a lot also depends on who you are punching and how she or he is reacting.
Generally speaking, if you hit some at the side of the neck hard enough, it can cause fracture to cervical spine, which is extremely painful. It can immediately result in difficulty in moving arms and torso. Also, there could be serious drop in blood pressure.
A punch on the front of the neck can crush your larynx and trachea that can cause breathing problem. If the punch is hard enough, it can cause you choke and also fracture hyoid ***** which can cause a heart *****.
Punching at the back of the neck can damage the cervical vertebrae. It will cause immediate headache, which will increase as the time passes if left untreated. The person will be left unconscious. Also, if the punch is too powerful, it could separate spine from the skull, which can cause death.
Already mentioned though, a person taking the punch can survive even the hardest hits with the right technique. After all, MMA fighters sustain such punches regularly.