Final answer:
The antonym of 'unassuming' is 'pretentious' which describes someone who is showy or artificially inflates their own importance, as opposed to the modesty implied by 'unassuming'.
Step-by-step explanation:
The antonym of 'unassuming' is 'pretentious'. When we discuss antonyms, we are looking at words that have opposite meanings. The word 'unassuming' refers to a person who is not pretentious or self-asserting; in other words, someone who is modest and does not seek to draw attention to themselves. An unassuming individual might be content with blending into the background and is not demanding of attention or admiration.
In contrast, a 'pretentious' individual typically presents themselves as being more important, successful, or knowledgeable than is actually the case. This person might embellish their accomplishments or engage in display meant to impress others, thus being the exact opposite of unassuming. Other words that could also serve as antonyms to 'unassuming' include 'arrogant', 'conceited', and 'ostentatious', but 'pretentious' captures the essence most directly.
In everyday situations, if someone is described as being unassuming, they are likely appreciated for their humility and simplicity. Conversely, if someone is called pretentious, it can be a critique of their behavior or attitude being seen as showy or artificially inflated.