The phrase "am one back" implies being one step behind or lagging behind others. The antonyms for this phrase can include terms such as "ahead," "leading," "first," or "in front." These antonyms denote being at the forefront or taking the lead position in a given situation. Another antonym for "am one back" could be "equal," which suggests being on par with others or at the same level as the rest of the group. In contrast, "am one back" suggests falling behind or having a relative deficiency in comparison to others. Knowing the antonyms of a word or phrase can help us express ourselves more precisely and accurately.