Antonyms for the phrase "most upfront" can include words such as dishonest, deceitful, obscure, evasive, and ambiguous. These words convey a sense of hidden agendas, intentional vagueness, and reluctance to disclose full information. Individuals who are dishonest and deceitful tend to mislead and manipulate others with false information, causing mistrust and discord. Obscure and evasive individuals often avoid answering direct questions, leaving others unclear about their intentions. In contrast, individuals who are transparent and forthright with information engender trust and confidence in their character and intentions. Therefore, using antonyms for "most upfront" can help to describe people as dishonest or obscure depending on how they choose to communicate information.