This is the 6399th most frequent Russian word.
чемпион
Champion.
In this context, 'чемпион' is metaphorically used to describe the feeling of accomplishment similar to that of being a champion.
Она чувствует себя чемпионом, выиграв важный матч.
She feels like a champion after winning an important match.
In this sentence, 'чемпион' is used to denote a person who has won a title or competition.
Мой брат — чемпион по теннису.
My brother is the champion in tennis.
Here, 'чемпион' is used to express the title or status that people aim to achieve.