The antonyms for the word "under-mined" are many and varied, depending on the context in which the term is used. Some possible antonyms include fortified, reinvigorated, strengthened, reinforced, and supported. These words suggest a sense of resilience and stability that is the opposite of being under-mined. Other possible antonyms include steadfast, unyielding, firm, solid, and unwavering, which suggest a sense of determination and integrity that is the opposite of being weak and vulnerable. Ultimately, the best antonyms for under-mined depend on the context of the situation and the needs of the individual or group involved.