17
formidable(adjective, tough, awful, terrible, fear)
13
dire(adjective, tough, difficult, awful, terrible)
10
fearful(adjective, tough, difficult, awful, terrible)
9
gruesome(adjective, awful, terrible, dreadful)
8
appalling(adjective, tough, difficult, awful, terrible)
8
terrible(adjective, tough, difficult, awful, fear)
8
ghastly(adjective, awful, terrible, fear, dreadful)
7
dreadful(adjective, tough, difficult, awful, terrible)
7
frightful(adjective, tough, difficult, awful, terrible)
7
horrible(adjective, tough, difficult, awful, terrible)
7
horrid(adjective, fear)
7
horrific(adjective, tough, difficult, awful, terrible)
6
direful(adjective, fear)
6
awful(tough, difficult, terrible, fear, dreadful)
6
illustrious(adjective, respect, knowledge)
6
tremendous(adjective, tough, difficult, awful, terrible)
6
dread
6
grim(awful, terrible, dreadful, ominous)
6
grisly(awful, terrible, strange, dreadful, horrifying)
6
horrendous(adjective, awful, terrible, dreadful)
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APASmart Define. (2016). redoubtable thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/redoubtable/thesaurus/synonyms
ChicagoSmart Define. 2016. "redoubtable thesaurus" https://smartdefine.org/redoubtable/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2016, redoubtable thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/redoubtable/thesaurus/synonyms>.
MLASmart Define. "redoubtable thesaurus" 2 March 2016. Web. 20 September 2026. <https://smartdefine.org/redoubtable/thesaurus/synonyms>