6
trying(adjective, tough, severe, rough, difficult)
6
vigorous(adjective, strong, prevailing, influential, commanding)
6
weighty(adjective, severe, harsh, heavy, painful)
5
all-powerful(adjective, tough, difficult, overwhelming, prevailing)
5
complex(adjective, hard, difficult, delicate, heavy)
5
direful(adjective, fear)
5
dismaying(adjective, difficult, horrible, overwhelming, terrifying)
5
exacting(adjective, tough, severe, rough, difficult)
5
grisly(adjective, appearance, awful, terrible, shocking)
5
gruesome(adjective, appearance, awful, terrible, shocking)
5
harsh(adjective, hard, great, severe, rough)
5
indomitable(adjective, difficult, overwhelming)
5
influential(adjective, powerful, prevailing, commanding)
5
labored(adjective, tough, severe, difficult, heavy)
5
stiff(adjective, great, tough, severe, difficult)
5
sturdy(adjective, strong, prevailing, influential, commanding)
5
ticklish(adjective, bad, hard, tough, difficult)
5
titan(adjective, feature, characteristic, size)
5
tricky(adjective, hard, tough, difficult, complex)
5
troublesome(adjective, hard, tough, severe, evil)
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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>