Antonyms for the word "trueheartednesses" can be difficult to find, as it is a relatively obscure or complex term. However, some possible antonyms might be insincerity, duplicity, or falsehood. These negative qualities indicate a lack of trustworthiness or honesty, which is the opposite of trueheartedness. Other antonyms for trueheartednesses could include betrayal, disloyalty, or treachery, which all suggest a breach of trust or commitment. Overall, antonyms for trueheartednesses represent qualities that are counterproductive to healthy relationships and undermine the foundations of trust and respect that are essential for meaningful connections.