There are several synonyms for the word "more unsustained" that can help convey a similar meaning. For instance, "unfounded," "unsupported," and "baseless" all suggest that a claim or argument lacks evidence or proof. "Groundless" and "unsubstantiated" are additional synonyms that convey a sense of weakness or fragility in a claim. "Unproven" and "unverified" indicate that something has not been adequately tested or confirmed. Overall, these synonyms emphasize the lack of support or credibility for a claim, suggesting that it should be regarded with skepticism or caution.