139 entries under tough topic. ×

20
stern(adjective, appearance, mean, severe)
20
unshakable(adjective, mean, hard, certain)
19
hard(adjective, mean, strong, severe)
19
remorseless(adjective, animal, mean, severe)
16
cruel(adjective, appearance, mean, strong, hard)
16
hard-nosed(adjective, mean, strong, hard)
16
unforgiving(adjective, mean, hard, severe)
15
severe(adjective, appearance, mean, strong, hard)
15
unremitting(adjective, hard, harsh, determined)
14
dogged(adjective, appearance, mean, hard)
14
ruthless(adjective, animal, appearance, mean, hard)
13
iron(noun, adjective, mean, hard)
13
merciless(adjective, appearance, mean, hard)
12
stiff-necked(adjective, mean, strong, hard)
11
pertinacious(adjective, strong, cold, determined)
11
pitiless(adjective, animal, mean, hard)
10
set in stone(expression, adjective, idiom, mean, hard)
10
unmerciful(adjective, mean, hard, severe)
9
mulish(adjective, mean, strong, hard)
9
steely(adjective, strong, hard, determined)
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APASmart Define. (2015). unrelenting thesaurus. Retrieved September 30, 2026, from https://smartdefine.org/unrelenting/thesaurus/synonyms
ChicagoSmart Define. 2015. "unrelenting thesaurus" https://smartdefine.org/unrelenting/thesaurus/synonyms (accessed September 30, 2026).
HarvardSmart Define 2015, unrelenting thesaurus, Smart Define, viewed 30 September, 2026, <https://smartdefine.org/unrelenting/thesaurus/synonyms>.
MLASmart Define. "unrelenting thesaurus" 3 August 2015. Web. 30 September 2026. <https://smartdefine.org/unrelenting/thesaurus/synonyms>