The antonyms for the word "was faithful" would be disloyal, unfaithful, betraying, treacherous, untrue. These words indicate the opposite meaning and characteristic of faithfulness. Being unfaithful means breaking the trust and commitment made to someone or something. Betraying someone's trust can lead to significant consequences, such as loss of respect, broken relationships, and damaged reputation. Treachery and disloyalty towards someone or something is not only immoral but also unethical. Hence, it is always essential to remain faithful and honest in all relationships, be it personal or professional, to build trust and respect in our lives.