"This is the stupidest thing you.ve ever done," she said.
Letting you go was the stupidest thing.
Bates (The Naturalist on the Amazons), " is one of the stupidest animals I ever met.
Formerly in Anna Pavlovna's presence, Pierre had always felt that what he was saying was out of place, tactless and unsuitable, that remarks which seemed to him clever while they formed in his mind became foolish as soon as he uttered them, while on the contrary Hippolyte's stupidest remarks came out clever and apt.
"Helene, who has never cared for anything but her own body and is one of the stupidest women in the world," thought Pierre, "is regarded by people as the acme of intelligence and refinement, and they pay homage to her.