The word un-exceptionable implies something that is beyond reproach, faultless, or flawless. A suitable antonym for this word would be "imperfect" or "faulty." These words indicate that something falls short of what is expected or desired, whether in quality, performance, or appearance. Another antonym could be "objectionable," meaning that something is offensive, unpleasant, or disagreeable. This may refer to behavior, opinions, or words that are deemed inappropriate, insulting, or discriminatory. Overall, there are many words that could serve as antonyms for un-exceptionable, depending on the context and the specific meaning intended.