77 entries under severe topic. ×

43
heavy(adjective, feature, characteristic, tough)
39
herculean(adjective, feature, characteristic, tough)
38
immense(adjective, feature, characteristic, great, tough)
13
onerous(adjective, tough, difficulty, difficult)
13
arduous(adjective, tough, difficulty, rough)
12
tough(adjective, strong, difficulty, rough)
12
laborious(adjective, tough, difficulty, rough)
11
difficult(adjective, hard, tough, evil)
10
hard(adjective, tough, evil, difficulty)
10
burdensome(adjective, tough, difficult, heavy)
10
menacing(adjective, bad, tough, unpleasant)
10
strenuous(adjective, tough, rough, difficult)
8
toilsome(adjective, tough, difficulty, difficult)
8
uphill(adjective, tough, rough, difficult)
7
demanding(adjective, tough, rough, difficult)
7
effortful(adjective, tough, difficult, heavy)
6
rugged(adjective, hard, evil, rough)
6
challenging(adjective, tough, difficult, awkward)
6
dangerous(adjective, hard, tough, evil)
6
grim(adjective, appearance, bad, manner)
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APASmart Define. (2015). formidable thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/formidable/thesaurus/synonyms
ChicagoSmart Define. 2015. "formidable thesaurus" https://smartdefine.org/formidable/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2015, formidable thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/formidable/thesaurus/synonyms>.
MLASmart Define. "formidable thesaurus" 17 July 2015. Web. 20 September 2026. <https://smartdefine.org/formidable/thesaurus/synonyms>