Probably it depends at least as much on context (the sum of all your interactions) as on how you present any single critique -- I know that I can take a piece o

Probably it depends at least as much on context (the sum of all your interactions) as on how you present any single critique -- I know that I can take a piece of criticism very differently depending on who is giving it, and that's not just a function of our formal relationship or their position in the hierarchy. So making a point of being sincerely positive whenever appropriate might help, even if you don't have anything good to say while delivering a rebuke. Also it's important to take into account each individual's temperament: try to learn which ones will be scared straight by a gentle word (and discouraged by anything more than that), and which ones need the severity of their mistakes hammered home. Also where they fall on the 'respect = unvarnished honesty' versus 'respect = niceness and politeness' spectrum. If you were calling me out on a big mistake, it would definitely be important to control any emotions like exasperation or bafflement, and focus in a matter-of-fact way on what happened/why it was a mistake/what to do next time.