2
difficile(adjective, tough, severe, rough, difficult)
2
distressing(adjective, bad, tough, severe, rough)
2
dominant(powerful, prevailing, influential, commanding)
2
effectual(prevailing, influential, commanding)
2
exhausting(adjective, hard, tough, severe, rough)
2
fantastic
2
fatal(adjective, dangerous)
2
fateful(adjective, tough, severe, important, significant)
2
firm(adjective, strong)
2
freaky
2
ghoulish(awful, terrible, dreadful)
2
grievous(adjective, tough, severe, difficult, unpleasant)
2
grinding(adjective, tough, severe, rough, difficult)
2
husky(adjective, strong)
2
intricate(adjective, hard, tough, severe, difficult)
2
lurid(adjective, awful, terrible, shocking, dreadful)
2
macabre(awful, terrible, shocking, dreadful, upsetting)
2
mammoth(adjective, difficult, overwhelming)
2
mettlesome(adjective, strong)
2
morbid(awful, terrible, shocking, dreadful, upsetting)
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APASmart Define. (2015). formidable thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/formidable/thesaurus/synonyms
ChicagoSmart Define. 2015. "formidable thesaurus" https://smartdefine.org/formidable/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2015, formidable thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/formidable/thesaurus/synonyms>.
MLASmart Define. "formidable thesaurus" 17 July 2015. Web. 21 September 2026. <https://smartdefine.org/formidable/thesaurus/synonyms>