The phrase "most unstinging" can be a tricky one to find antonyms for since it is an unusual combination of words. However, some possible antonyms could include words like painful, stinging, critical, or harsh. These antonyms would describe situations where the phrase "most unstinging" would not apply, such as a painful injury or a harsh critique. Other antonyms might include unkind, merciless, unsympathetic, or brutal. It is important to note that since "most unstinging" is a relatively uncommon phrase, there may not be a perfect antonym that fits in every context.