I used to have an assistant who couldn't take criticism in any form. No matter how I would spin it, she would get defensive and the backlash could last for days.
As a motivational speaker, I love the Toastmasters' method to deliver feedback. Toastmasters teaches you to evaluate a speaker by layering positive feedback with opportunity for improvement followed by positive feedback again. Overall this feedback strategy works well- unless you are dealing with my assistant. She was onto my motivational strategies and wouldn't take it. Any opportunity to improve could never penetrate her wall of indifference.
Here is a feedback strategy that helped her finally take responsibility...
I had to catch her in a mistake, rewind, go through what had happened step by step and help her recognize her contribution to the error. I didn't point fingers or assign blame, but facts are facts. Overall, mistakes happen for a reason, so I pointed them out over and over until she recognized her part in the problem.
Results were subtle at first, but eventually certain behavior patterns reversed and her productivity improved. Given her cynical personality, positive feedback backfired as she assessed it as motivational hogwash. I cut the feedback and built a case on facts.
As a motivational speaker I prefer to work with an inspired, positive and fun staff, whose values are in line with mine. When we cut our ties a couple of years later, she was one of my most productive assistants.
Dealing with difficult people is a continuous process of give and take. Most people have some difficult qualities, and it's a matter of searching for common ground and agreeing to work out issues in a straight forward, proactive way.
How do you motivate people who don't respond to positive feedback?
Funny guest motivational speaker strategies to Deal with Sarcasm