Synonyms of the word

formidable

• adj. Causing fear, dread, awe, or discouragement as a result of size, strength, or some other impressive feature;…
• adj. Difficult to defeat or overcome.

alarming

• v. present participle of alarm.
• adj. causing apprehension, fear or alarm; frightening.

impressive

• adj. Making, or tending to make, a positive impression; having power to impress.
• adj. Capable of being impressed.
• adj. Appealing.

redoubtable

• adj. Eliciting respect or fear; imposing; awe-inspiring.

unnerving

• v. present participle of unnerve.