The word "more inobnoxious" already means that something is becoming less harmful or offensive. However, if one were to look for antonyms of this phrase, they would be searching for words that imply a greater degree of offensiveness or harm. Some possible antonyms for "more inobnoxious" could be "more obnoxious," "more harmful," "more hurtful," "more offensive," and "more destructive." These words suggest that the subject in question is becoming more problematic, unpleasant or damaging in nature. So, while "more inobnoxious" implies a continuing decrease in offensiveness, its antonyms indicate an increase in disturbance or harm.