The word "un-beautiful" means something that is not beautiful or attractive. Therefore, the antonyms for this word would be the opposites of beauty, such as ugliness, unattractiveness, and plainness. Other antonyms include unpleasant, repulsive, and unsightly. On the positive side, "beautiful" has several antonyms, including ugly, unattractive, plain, and homely. These opposite words can be used to describe different aspects of a person's appearance or personality, and it's essential to choose the appropriate antonym depending on the context. In conclusion, the antonyms of "un-beautiful" can convey a range of negative attributes and characteristics that stand in contrast to beauty.