The term "most papistic" can be substituted with various synonyms depending on the context. "Papistic" refers to having the characteristics or beliefs of the Roman Catholic Church. Therefore, synonyms for "most papistic" could be "most Catholic," "most Vatican-supportive," or even "most ultramontane." Another possible synonym might be "most devout" or "most traditionalist," depending on the specific aspect of Catholicism being emphasized. However, it's important to note that the choice of synonym could significantly affect the tone and connotations of a piece of writing. Therefore, it's necessary to consider the intended meaning and impact of any potential replacement words.