Synonyms of the word 
UNNERVING → ALARMING - FORMIDABLE - REDOUBTABLE
unnerving
- v. present participle of unnerve.
alarming
- v. present participle of alarm.
- adj. causing apprehension, fear or alarm; frightening.
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.
redoubtable
- adj. Eliciting respect or fear; imposing; awe-inspiring.
If you are interested in words, visit the following sites :
- wiktionary.org/unnerving For complete definition of a word
- 1word.ws/unnerving to play with words, suffixs, prefixs, etc.