Antonyms for the word "best-quality" refer to the opposite of something that is of superior quality or standard. Some common antonyms for the term include poor quality, low-grade, substandard, inadequate, unsatisfactory, and mediocre. These antonyms describe things that are not up to par and lack the necessary elements to be considered top of the line. They are often associated with inferior products, services, or experiences, and are not recommended for those seeking the highest level of excellence. It's important to keep in mind that when searching for products or services, one should always strive to find the best quality available within their means, and avoid settling for anything less.