The antonyms for the word "under-achieving" are categorized into three main categories; Meeting expectations, Exceeding expectations, and Overachieving or Thriving. Under each category, there are several antonyms to "underachieving." Meeting expectations would include performing satisfactorily or sufficiently; meeting targets, meeting expectations of people, or just doing enough to keep up. Some antonyms falling under this category include "excelling," which means performing exceptionally well and "outperforming," meaning exceeding expectations. Exceeding expectations antonyms include "overachieving," "over-performing," and "thriving," while overachieving antonyms include "overshooting," meaning doing more than is necessary, and "overreaching," meaning venturing beyond one's capabilities.