Antonyms for the word "most attested" could include "least verified," "unproven," "unsubstantiated," "untested," "uncorroborated," "unconfirmed," or simply "less attested." These antonyms suggest a lack of evidence or proof to support the particular claim or assertion in question, as opposed to the strong historical or empirical evidence that typically accompanies something that is "most attested." While it is important to evaluate evidence on a case-by-case basis and avoid making sweeping generalizations about the trustworthiness of certain sources or claims, it is also important to exercise caution and skepticism when encountering claims that lack strong corroborating evidence.