The opposite of "most unforthcoming" could be described as "very forthcoming," "open," or "communicative." These antonyms indicate an individual who willingly shares information and is forthcoming with their thoughts, feelings, and opinions. Other antonyms for "most unforthcoming" may include "outspoken," "candid," "voluble," and "communicative." Such individuals may be considered approachable, social, and easy to talk to. Compared to those who are unforthcoming, individuals who are forthcoming provide a more stimulating conversation, encourage dialogue and have a stronger sense of transparency, honesty, and accountability.