The antonyms for "more truehearted" would be "disloyal," "untrustworthy," "faithless," "treacherous," "perfidious," and "false." Individuals who possess these traits lack the sincerity, loyalty, and trustworthiness associated with being truehearted. They may deceive or betray others, breaking promises and failing to honor commitments. Being truehearted requires honesty, integrity, and a strong sense of responsibility towards others, whereas being disloyal or untrustworthy shows a lack of respect for others and their feelings. Therefore, it is important to choose our words and actions carefully to ensure we do not fall into the category of being untrue or disloyal.