How many letters does the top answer for “so surprisingly impressive as to stun or overwhelm” have?

The most common answer is astonishing (11 letters).

Crossword clue: so surprisingly impressive as to stun or overwhelm

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

astonishing 11 letters wn-def

so surprisingly impressive as to stun or overwhelm

staggering 10 letters wn-def

so surprisingly impressive as to stun or overwhelm