150 entries under hard topic. ×

3
serious(adjective, close, strong, tough)
3
barbarous(adjective, animal, appearance, mean, strong)
3
cold-blooded(adjective, mean, evil, nasty)
3
forbidding(adjective, appearance, strong, tough)
3
hard-line(adjective, strong, tough, firm)
3
indurate(adjective, mean, determined, resolute)
3
mean(adjective, animal, severe, nasty)
3
perverse(adjective, mean, tough, determined)
3
tyrannical(adjective, tough, evil, nasty)
3
uncompassionate(adjective, animal, mean, harsh)
3
uncooperative(adjective, mean, persistent, obstinate)
3
unregenerate(adjective, tough, harsh, cruel)
3
vindictive(adjective, mean, tough, severe)
2
astringent(adjective, close, strong, tough)
2
authoritarian(adjective, strong, tough, severe)
2
cold(adjective, close, mean, strong)
2
cold-hearted(adjective, cold, cruel, unfeeling)
2
dog-eat-dog(adjective, mean, severe, harsh)
2
gruff(adjective, severe, sharp, nasty)
2
hard-core(adjective, strong, tough, severe)
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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>