Soft-headed is an adjective that refers to someone who is foolish or lacking in intelligence. Some of the antonyms for the word soft-headed are wise, intelligent, and smart. A wise person is someone who has a deep understanding of various subjects, and is able to make good decisions based on their knowledge and experience. An intelligent person has a high level of mental ability, and is able to think, reason, and solve problems quickly and effectively. A smart person is someone who has a good sense of judgment, and is able to make sound decisions even in challenging situations. Therefore, these antonyms can be used to describe someone who possesses good judgment, intelligence, and wisdom.