All 4 Uses

formidable
in
The Call of the Wild
(Edited)

This accomplished, the outfit, though cut in half, was still a formidable bulk.
p. 105.3

formidable = intimidating or impressive
His cunning was wolf cunning, and wild cunning; his intelligence, shepherd intelligence and St. Bernard intelligence; and all this, plus an experience gained in the fiercest of schools, made him as formidable a creature as any that intelligence roamed the wild.
p. 166.5 *

formidable = intimidating
Buck had already dragged down a stray part-grown calf; but he wished strongly for larger and more formidable quarry, and he came upon it one day on the divide at the head of the creek.
p. 168.9

formidable = intimidating or impressive
He was in a savage temper, and, standing over six feet from the ground, was as formidable an antagonist as even Buck could desire.
p. 169.2

Definitions:

(1) (formidable)
intimidating or impressive -- arousing fear or admiration due to impressiveness or challenge
(2) (meaning too rare to warrant focus)