The opposite of "un-tended" is tended, which refers to something that has been given the necessary care and attention it requires. To tend means to maintain or take care of something, and antonyms for un-tended include cared for, maintained, looked after, tended to, nurtured, and cultivated. A garden that is tended to will thrive with healthy plants and vegetables. Similarly, a well-tended animal will be healthy and thrive in good conditions. Whether it's a garden, animal, or person, tending to their needs is crucial for their survival and growth. Therefore, it's important to make sure that we keep a lookout for things that require attention and give them the care they need.