Untrustier is a negative word that means not trustworthy. There are several other synonyms that can be used instead of untrustier such as unreliable, unfaithful, disloyal, deceitful, treacherous, and dishonest. Someone who is considered untrustier may lack the necessary moral qualities to be reliable, or they have a track record of being disloyal to their commitments or promises. Using synonyms like unreliable or disloyal instead of untrustier can help to soften the negative connotation that the word carries, while still conveying the same meaning. Overall, it is important to use synonyms that accurately reflect the context of the situation.