2
haunting
2
immutable(adjective, set, hard, stiff, persistent)
2
importunate
2
inalterable(adjective, inflexible)
2
indifferent(adjective, rocky, pebbly, flinty)
2
indomitable(adjective, set, strong, hard, tough)
2
industrious
2
inhumane(adjective, animal, mean, hard, tough)
2
insensitive(adjective, hard, tough, harsh, cruel)
2
interminable(adjective, determined, steady, resolute, persistent)
2
invariable(adjective, severe, harsh, solid, certain)
2
ironclad
2
long
2
loyal
2
macabre
2
malevolent(adjective, mean, evil, nasty, harsh)
2
mean(adjective, animal, hard, severe, nasty)
2
mordant
2
nagging
2
never-ending(determined, constant, obstinate, continuous, endless)
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APASmart Define. (2015). unrelenting thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/unrelenting/thesaurus/synonyms
ChicagoSmart Define. 2015. "unrelenting thesaurus" https://smartdefine.org/unrelenting/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2015, unrelenting thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/unrelenting/thesaurus/synonyms>.
MLASmart Define. "unrelenting thesaurus" 3 August 2015. Web. 27 September 2026. <https://smartdefine.org/unrelenting/thesaurus/synonyms>