The antonyms of the phrase "most pretensionless" could include words such as "ostentatious," "pretentious," "showy," "flashy," "arrogant," or "conceited." These words all refer to individuals or actions that exhibit excessive or overbearing behavior, often in an attempt to impress others or portray oneself in a favorable light. In contrast, being pretensionless implies a lack of such qualities, and instead suggests honesty, simplicity, and modesty. By avoiding pretentious behavior, individuals can foster more genuine relationships with others, and avoid the negative consequences that often come with excessive self-promotion.