Wordgenius says, “A deuteragonist isn’t necessarily the same from one story to the next. A deuteragonist may be on the protagonist’s side, like a sidekick or a love interest. Or they can be a villain, foil, or primary rival the protagonist must defeat. The deuteragonist can simply serve a neutral role, too.”
If one of my students finishes second in anything, I will call him or her a deuteragonist. After all, there is agony in finishing anything but first.