not even; not any ~
A formal, literary pattern meaning 'not even (one)' or 'not any', used to emphasize that even the smallest amount is not permitted or possible.
たりとも is a stiff, written-style expression that appears almost exclusively in formal contexts like speeches, legal documents, or literary prose. It combines with a minimal quantity—usually 'one' of something—to assert that not even that smallest unit is allowed or possible. The phrase is always followed by a negative or a prohibitive statement, creating a forceful 'not even one' nuance. For example, 一人たりとも許さない means 'I won't forgive even one person.'