by a long shot
by a long shot {adv. phr.}, {informal}
By a big difference; by far. — Used to add emphasis.
Bert was the best swimmer in the race, by a long shot.
Often used with a negative.
Tom isn't the kind who would be fresh to a teacher, by a long shot.
Our team didn't win — not by a long shot.
Compare: MISS BY A MILE.
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Source: A Dictionary of American Idioms