70 entries under hard topic. ×

19
painful(adjective, difficult, complex)
19
problematic(adjective, difficult, complex)
19
sensitive(adjective, difficult, complex, subtle)
19
toilsome(adjective, difficult, complex)
19
unbearable(adjective, difficult, complex)
18
sad(adjective, difficult, complex, greatness)
18
dire(adjective, difficult, complex)
18
extreme(adjective, strong, great, sharp)
18
labyrinthine(adjective, difficult, complex)
18
leaden(adjective, difficult, complex)
18
massive(adjective, difficult, complex)
18
ponderous(adjective, difficult, complex)
18
sheer(adjective, difficult, complex)
15
unfathomable(adjective, complete, obscure, difficult)
13
great(adjective, strong, intense, powerful)
11
obscure(adjective, complex, deep, mysterious)
10
subtle(adjective, quiet, slight, fine)
9
mysterious(adjective, obscure, delicate, complex)
8
strong(adjective, strong, great, sharp)
7
enigmatic(adjective, obscure, deep, tricky)
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APASmart Define. (2016). profound thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/profound/thesaurus/synonyms
ChicagoSmart Define. 2016. "profound thesaurus" https://smartdefine.org/profound/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2016, profound thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/profound/thesaurus/synonyms>.
MLASmart Define. "profound thesaurus" 26 February 2016. Web. 24 September 2026. <https://smartdefine.org/profound/thesaurus/synonyms>