Bad-mannered refers to a person who behaves rudely and discourteously. Antonyms for bad-mannered would be words that describe a person who is well-behaved, courteous, and polite. The first antonym that comes to mind is well-mannered, which means having good manners and behavior. Another antonym is polite, which means showing sensitivity towards others and understanding their needs. Respectful is another antonym that describes a person who displays courteous behavior towards others. Other antonyms for bad-mannered include polite, courteous, gracious, genteel, and refined. It's essential to remember that displaying good manners is essential to building positive relationships with others, and being polite and respectful can go a long way in life.