Without issue is a phrase that implies the absence of problems, difficulties, or obstacles. However, there are several antonyms that can be used to describe the opposite of this phrase. Some common antonyms for without issue are problematic, troublesome, challenging, complicated, difficult, and controversial. These words suggest that there are hurdles or complications in the situation at hand, making it hard to resolve or solve. Other antonyms that convey similar ideas include difficult, thorny, knotty, awkward, and sticky. Using these antonyms can help provide a more accurate description of the situation, providing context and depth to the conversation.