The antonyms for the phrase "most sub-par" can be labelled as exceptional, outstanding, excellent, superior, superb, supreme, unparalleled, extraordinary, incomparable, top-notch, and flawless. The phrase "most sub-par" is often used in a negative context to indicate poor quality or performance. Thus, using its antonyms can help you express a positive perspective. For instance, when you describe a product as "outstanding," you are communicating that this product is of high quality and exceptional value. Similarly, using terms like "superb" and "top-notch" express the idea that the item or performance is of superior quality or excellent in every way.