(1) No government can be long secure without a formidable opposition. 

(2) In debate he was a formidable opponent.

(3) Competition from established businesses can be formidable.

(4) The task was a formidable one.

(5) She has a formidable intellect.

(6) They had to overcome formidable obstacles.

(7) We have a formidable task ahead of us.

(8) The two players together make a formidable combination.

(9) He met with a woman with a formidable appearance.

(10) She has a formidable list of qualifications.

(11) The building is grey, formidable, not at all picturesque.

(12) Somehow the small but formidable woman fought her way through the crowd to reach her son.

(13) The head of the research section was a formidable old professor.

(14) The task looks formidable.

(15) There are formidable obstacles on the road to peace.

(16) He was a four-square and formidable hero.

(17) There's no formidable obstacles in the world.

(18) He fronted a formidable band of fighters.

(19) The new range of computers have formidable processing power.

(20) He remained a formidable opponent.

(21) He had a formidable stage presence.

(22) Monsieur Valentin was a formidable political operator.

(23) The elderly are a formidable force in any election.

(24) The customer is faced with a formidable array of products. Sentencedict.com

(25) Marsalis has a formidable reputation in both jazz and classical music.

(26) She was one of the most formidable intellects of her time.

(27) An army of stags led by a lion would be more formidable than one of lions led by a stag. 

(28) A good head and a good heart are always a formidable combination.

(29) She was once a political nonentity, but has since won a formidable reputation as a determined campaigner.

(30) He worked in the property business for a number of years, acquiring a reputation as a formidable wheeler-dealer.