The antonyms for "were unfaithful" are loyal, faithful, devoted, trustworthy, committed, and dedicated. These words hold the opposite meaning of being disloyal or dishonest towards someone. Loyalty reflects the quality of being reliable and supportive in a relationship. Similarly, faithfulness is a quality of being true to one's word or promise, while devotion refers to strong attachment or dedication to a person, duty, or cause. Trustworthiness implies having the capability of being trusted, while commitment reflects the determination to follow through a task, responsibility, or relationship. Finally, dedication involves the complete surrender and devotion to a cause or relationship.