A line that no parent should ever cross when you punishing a child is psychical, emotional and psychological abuse. Wheter for toddlers or teens, its all the same. We are all human and children are the most vulnerable human because they are just starting their life. They don't know what their doing. Not saying that parent or any other adult does, but when you grow up with your personal expriences moral valuse and attidues, they know way more than a child. Maybe if your child is in danger or going to do something real stupid, you pull them out or shout to get their attetnion would work but that's probably the only time. In simple words, psyhical (hitting, slapping, breating, throwing objects, using objects) instills fear. Sure you get them ti stop but they wouldnt want to come to you when they have problems or did something stupid as their scared that paernts will react badly which leads to sneakniess, delquiency and end up in dangerous situations. Emtionally (threating, hurtful words, insulting humilating and so on) and psycholgically (emtional maniputltion, blackmailing, narccism, blaming ) will just make them feel stupid, embraaed and ashamed of what they did. It might stop them from doing it but it also could lead to mental problems.