The antonyms of "most good mannered" would include "ill-mannered," "impolite," "disrespectful," "rude," "discourteous," "uncivil," "impudent," "crass," "vulgar," and "uncouth." Someone who is ill-mannered may be impolite and lacking in civility, while someone who is impudent may be rude and disrespectful. The opposite of good manners is bad manners, which can take many forms. It is important to remember that good manners are not just about following strict rules of social etiquette but also about treating others with kindness and respect. Therefore, cultivating good manners is an important aspect of forming positive relationships with others.