When it comes to the antonyms of the word "unstressful," there are several words that come to mind. The opposite of unstressful can be stressful, demanding, nerve-wracking, taxing, difficult, anxious, hectic, intense, and high-pressure. Each of these words signifies a state of being that is the opposite of unstressful, where one is prone to experiencing anxiety, tension, and pressure. While some people may thrive in these environments, others may find it challenging to manage their stress levels. Therefore, it's important to recognize when one is feeling stressed and take steps to alleviate the tension before it becomes overwhelming.