without a shadow of a doubt
Definitions
With absolute certainty; completely free from any doubt.
In a manner that is beyond any question or dispute.
Examples
She knew without a shadow of a doubt that she had made the right decision.
Without a shadow of a doubt, he is the most talented musician in the orchestra.
Synonyms
beyond any reasonable doubt certainly indisputably unquestionably definitely beyond a shadow of a doubt
Antonyms
doubtfully uncertainly questionably dubiously perhaps possibly