137 entries under tough topic. ×

4
flinty(adjective, close, strong, hard)
4
hard-shell(adjective, strong, hard, severe)
4
hardened(adjective, hard, harsh, cold)
4
pigheaded(adjective, mean, hard, determined)
4
staunch(adjective, strong, firm, determined)
3
serious(adjective, close, strong, hard)
3
barbarous(adjective, animal, appearance, mean, strong)
3
cussed(adjective, severe, firm, unreasonable)
3
forbidding(adjective, appearance, strong, hard)
3
hard-line(adjective, strong, hard, firm)
3
persisting(adjective, strong, firm, determined)
3
perverse(adjective, mean, hard, determined)
3
true(adjective, strong, firm, determined)
3
tyrannical(adjective, hard, evil, nasty)
3
unregenerate(adjective, hard, harsh, cruel)
3
vindictive(adjective, mean, hard, severe)
2
astringent(adjective, close, strong, hard)
2
authoritarian(adjective, strong, hard, severe)
2
cantankerous(firm, persistent, obstinate, stubborn)
2
contumacious(firm, persistent, obstinate, stubborn)
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APASmart Define. (2015). relentless thesaurus. Retrieved September 29, 2026, from https://smartdefine.org/relentless/thesaurus/synonyms
ChicagoSmart Define. 2015. "relentless thesaurus" https://smartdefine.org/relentless/thesaurus/synonyms (accessed September 29, 2026).
HarvardSmart Define 2015, relentless thesaurus, Smart Define, viewed 29 September, 2026, <https://smartdefine.org/relentless/thesaurus/synonyms>.
MLASmart Define. "relentless thesaurus" 24 June 2015. Web. 29 September 2026. <https://smartdefine.org/relentless/thesaurus/synonyms>