This is the 2424th most frequent Russian word.
победителем
Winner.
Here, 'победителем' (winner) is used as a predicate nominative to describe the subject's status as the winner.
Он стал победителем в соревновании.
He became the winner in the competition.
In this context, 'победителем' is used in the instrumental case to denote the resulting role or title attributed to someone.
Победителем окажется тот, кто решит задачу первым.
The winner will be the one who solves the problem first.
Although 'победителем' itself is not used directly in this sentence, it clarifies usage where it often relates to the individual being acknowledged or described as a winner.