The antonyms for the phrase "more doubtless" can be phrases like "less certain," "more questionable," or "less likely." These antonyms suggest an absence of surety or confidence, and imply a lack of belief in the likelihood of a certain outcome. Other antonyms may include "less probable," "more hesitant," or "less decisive." While the phrase "more doubtless" suggests a high degree of certainty, antonyms invoke an opposite connotation, indicating an atmosphere of doubt, skepticism, or skepticism. By using antonyms for "more doubtless," we can shift the tone of our language and express different shades of meaning and intentions.