R.M.
It felt like you were describing my son when I read this, you'd tell him no and he'd do it again with a smile on his face. The only thing we found that would work is to restrain him. I know that sounds harsh but I felt it was better than a spanking that didn't work anyway. I'd hold him in my lap and hold his arms down even though he'd scream and fight and wouldn't let go until he calmed down. It takes time and patience, but eventually it didn't take to much to get him to calm down and stop hitting. It seems he eventually got sick of being restrained and quit hitting. My granddaughter has recently started pinching her mother's face when she is upset and her mother is restraining her as well. Just a tight hug so to speak and it seems to work. She calms down relatively quickly and doesn't pinch a second time.