Antonyms of adj formidable

2 senses of formidable

Sense 1
formidable -- (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")

INDIRECT (VIA impressive) -> unimpressive -- (not capable of impressing)

Sense 2
formidable, redoubtable, unnerving -- (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")

INDIRECT (VIA alarming) -> unalarming -- (not alarming; assuaging alarm)

Similarity of adj formidable

2 senses of formidable

Sense 1
formidable -- (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")
       => impressive (vs. unimpressive) -- (making a strong or vivid impression; "an impressive ceremony")

Sense 2
formidable, redoubtable, unnerving -- (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")
       => alarming (vs. unalarming) -- (frightening because of an awareness of danger)