The phrase "came in first" implies winning or succeeding in a competition, race, or event. Its antonyms would be phrases that indicate losing, failing, or being defeated. Some examples are: "came in last," "fell short," "lost," "finished behind," "was defeated," "didn't make the cut," "came up short," "missed out," and "was outpaced." These antonyms are often used to describe an individual or team's performance in sports, academic contests, or job-related tasks. Although coming in first is generally seen as positive, experiencing setbacks and failures can lead to growth and development.