11
malignant(adjective, mean, bad, evil, nasty)
11
noisome(adjective, bad, evil, offensive, immoral)
11
unhealthy(adjective, offensive, foul, disgusting, distressing)
11
unwholesome(adjective, offensive, foul, disgusting, unhealthy)
10
dangerous(adjective, bad, offensive, foul, harmful)
10
deadly(adjective, bad, evil, cruel, unkind)
8
disastrous(adjective, harmful, injurious, damaging, deadly)
8
malign(adjective, mean, bad, evil, nasty)
8
virulent(adjective, mean, bad, evil, nasty)
7
calamitous(adjective, harmful, injurious, damaging, deadly)
7
catastrophic(adjective, harmful, injurious, damaging, deadly)
7
lethal(adjective, bad, evil, harmful, injurious)
7
malicious(adjective, mean, bad, wrong, evil)
7
nocuous(adjective, cruel, negative, unkind, harmful)
7
not good
6
corrupt(adjective, evil, low, foul, vicious)
6
insalubrious(adjective, offensive, foul, disgusting, harmful)
6
unfavourable
6
venomous(adjective, mean, bad, evil, nasty)
5
fatal(adjective, bad, evil, harmful, injurious)
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APASmart Define. (2016). deleterious thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/deleterious/thesaurus/synonyms
ChicagoSmart Define. 2016. "deleterious thesaurus" https://smartdefine.org/deleterious/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2016, deleterious thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/deleterious/thesaurus/synonyms>.
MLASmart Define. "deleterious thesaurus" 24 March 2016. Web. 23 September 2026. <https://smartdefine.org/deleterious/thesaurus/synonyms>