The opposite of "most smoothspoken" would be "least articulate" or "most rough-spoken". While "most smoothspoken" connotes a person with a silver tongue, who can speak confidently and persuasively, the opposite suggests someone who stumbles over their words or struggles to convey their thoughts effectively. This could be due to nervousness, lack of confidence, or simple inexperience with public speaking. A person who is least articulate may come across as awkward, hesitant, or even untrustworthy. Therefore, it is important to develop one's communication skills to ensure that they can express their ideas clearly and with conviction.