undisputed champion

Translations
бесспорный чемпион
She became the undisputed champion after winning all the matches.
Она стала бесспорным чемпионом после победы во всех матчах.
Definitions
An undisputed champion is a titleholder in a sport or competition who is recognized as the sole champion without any contesting claims or rival champions, often due to having won all relevant titles or defeating all challengers.