I had to spank my daughter exactly ONCE. At approximately 18 months, she began kicking me in the stomach while changing her diaper. I told her "Stop that ! That hurts !". She laughed - and kicked me again. I said "If you do that again, I'm going to spank you." She laughed, and kicked me again - harder.
I hauled her off the bed and proceeded to spank - hard enough to insure plenty of tears.
Guess what ? She never needed another lesson. Sweet reason worked after that. It was the anithesis of injury - it was salutary. She was a much happier child because of it.
Ineffectual swats and finger shaking, along with screaming and time-outs, etc., are stupid. A few good hard whacks eliminates much future unhappiness.
Sheesh.