The antonyms for the word "more ill-founded" are numerous. For instance, "well-supported," "valid," "strong," "logical," and "reasonable" are all antonyms for "ill-founded." These words imply that the argument, idea or thought process is based on substantial and reliable evidence, as opposed to being flawed and unsupported. They reflect a sound and rational approach that is backed by facts and analysis. They stand in direct contrast to "ill-founded," which means the opposite, unsupported, and not factual. Using such antonyms can contribute to clear and concise communication, helping to avoid confusion and misunderstandings.