150 entries under hard topic. ×

17
cruel(adjective, appearance, mean, strong)
16
ruthless(adjective, animal, appearance, mean)
16
unforgiving(adjective, mean, tough, severe)
16
unremitting(adjective, adverb, tough, continue)
14
severe(adjective, appearance, mean, strong)
14
dogged(adjective, appearance, mean, strong)
14
hard-nosed(adjective, mean, strong, tough)
14
merciless(adjective, appearance, mean, tough)
13
iron(adjective, mean, strong, tough)
13
pitiless(adjective, animal, mean, tough)
11
savage(adjective, animal, mean, strong)
11
strict(adjective, strong, tough, severe)
10
austere(adjective, appearance, mean, strong)
10
fierce(adjective, animal, mean, tough)
10
stiff-necked(adjective, mean, strong, tough)
10
tough(adjective, mean, strong, severe)
10
unmerciful(adjective, mean, tough, severe)
9
inhuman(adjective, animal, mean, tough)
9
rigorous(adjective, strong, tough, severe)
9
set in stone(expression, adjective, idiom, mean)
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APASmart Define. (2015). relentless thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/relentless/thesaurus/synonyms
ChicagoSmart Define. 2015. "relentless thesaurus" https://smartdefine.org/relentless/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, relentless thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/relentless/thesaurus/synonyms>.
MLASmart Define. "relentless thesaurus" 24 June 2015. Web. 25 September 2026. <https://smartdefine.org/relentless/thesaurus/synonyms>