The word "more unpromising" suggests something that is bleak, uninviting, and discouraging. The antonyms for this word would describe something that is promising, engaging, and encouraging. For instance, instead of using the term "more unpromising," one could use words like hopeful, propitious, or auspicious, which indicate a favorable outcome or a positive outlook. Other antonyms that could be used for "more unpromising" include inspiring, optimistic, encouraging, upbeat, and favorable. So, whenever you want to describe something that is not very encouraging, you can use the antonyms for "more unpromising" to give a positive spin to your language.