The antonyms for the word "most unpurified" can be "most purified", "clean", "purified", "sterile", "sanitized", "sterilized", "clarified", "refined", "polished", "purged", "filtered", "disinfected", "decontaminated", "purified" and "treated". It means that the water, air, or any other substance which previously had impurities and toxins are now cleansed and free from all kinds of harmful substances. A purification process can cleanse water, air or material by removing impurities, contaminants, bacteria, viruses, and other harmful particles. Therefore, a purified substance is healthier and safer for consumption or use.