The word "unstrengthen" refers to the opposite of strengthening or making something stronger. Therefore, the antonyms for "unstrengthen" would include strengthening, fortifying, reinforcing, buttressing, enhancing, boosting, empowering, and building up. These terms indicate the act of making something stronger, firmer, or more robust. In contrast, "unstrengthen" implies weakening or making something vulnerable to breaking or failing. Therefore, the opposite terms emphasize the importance of building and enhancing the strength of something, such as a structure, a relationship, or one's personal resilience. Using antonyms for "unstrengthen" helps to convey the concept of positive reinforcement and growth.