This Harvard Business Review article by Marcus Buckingham and Cisco’s Ashley Goodall is a master class in the theory and practice of effective feedback. It’s long but worth the read.
Some of it is counterintuitive to modern business wisdom. It reminded me of St. Paul’s ancient charge to the church in Philippi:
Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things.
I think when that concept is married to the ancient Jewish proverb, “Faithful are the wounds of a friend,” leaders are an unstoppable force for good.