What level of criticism is generally perceived as innapropriate?

So (almost i guess) everyone perceives 'hierarchies' and some shame when they do not achieve some pre defined milestones in life (career, family, looks etc.). The problem obviously is with the intensity of shame in our case.

What helps me is to expand my tolerance to criticism. But my brain still needs some safety net. Like I generally cannot tell when a criticism is 'too much' and when it is appropriate. I do not want to be a doormat and accept being treated poorly. But I need help regarding what is 'too much' in terms of criticism. Like, what criticism that will determine ppl without NPD enforce a boundary?

Please only respond to that question. I do not have the capacity to tolerate criticism ( ;) )