No pain... None!

I'm not aware of a situation where making someone feel badly about their work or about themselves has ever enabled success. Guilt, ridicule, bullying, a condescending tone, doubt, hurtful criticism and anything that makes someone feel like they are not worthy of your confidence, we'll call "pain". I could call it anything, but pain seems appropriate. Pain and especially individually addressed personal pain has no upside.

If you have a relationship (personal or business) where you find that you need to deliver personal pain, you would be better off finding a way to end the relationship. Pain won't fix anything - it only destroys potential. I don't know of anyone who ever reached their potential without support and encouragement in the right places. Getting mad about something is one thing, but if the recipient takes your lack of confidence to heart, it's pretty much over.