Synonyms of formidable

Adjective

1. formidable, impressive (vs. unimpressive)

usage: extremely impressive in strength or excellence; "a formidable opponent"; "the challenge was formidable"; "had a formidable array of compositions to his credit"; "the formidable army of brains at the Prime Minister's disposal"

2. formidable, redoubtable, unnerving, alarming (vs. unalarming)

usage: inspiring fear; "the formidable prospect of major surgery"; "a tougher and more redoubtable adversary than the heel-clicking, jackbooted fanatic"- G.H.Johnston; "something unnerving and prisonlike about high grey wall"

Definition and meaning of formidable (Dictionary)