The word 'sub-normal' refers to something that is below the average standard. Antonyms for this word would be "superior", "exceptional", "excellent", "outstanding", "extraordinary", "remarkable", "outstanding", "superlative", "exceptional", "above average", "highly-competent" and "above par". These antonyms describe something that is better than the norm or average that is previously established. They are words that describe performance, abilities, or behaviors that are above the usual expectation. These antonyms are all positive words that depict qualities that are highly desirable in every aspect of life, be it in academia, professional work, sports, or personal endeavors.