14
suicidal(adjective, violent, cruel, harmful, injurious)
13
lethal(adjective, bad, evil, harmful, injurious)
13
prejudicial(adjective, bad, cruel, unkind, harmful)
13
malevolent(adjective, mean, bad, evil, nasty)
13
pestilent(adjective, help, bad, unhealthy, harmful)
12
dangerous(adjective, bad, offensive, foul, disgusting)
11
malign(adjective, mean, bad, evil, nasty)
11
pestilential(adjective, help, bad, evil, harmful)
11
sinister(adjective, bad, evil, nasty, negative)
10
mischievous(adjective, mean, bad, nasty, cruel)
10
pestiferous(adjective, bad, evil, harmful, injurious)
10
disadvantageous(adjective, cruel, unkind, contrary, distressing)
10
inimical(adjective, offensive, negative, foul, antagonistic)
10
wicked(adjective, mean, bad, evil, nasty)
9
nocuous(adjective, cruel, unkind, distressing, harmful)
9
venomous(adjective, mean, bad, evil, nasty)
8
noisome(adjective, bad, evil, offensive, immoral)
8
unwholesome(adjective, offensive, foul, disgusting, unhealthy)
7
mortal(adjective, bad, evil, grave, harmful)
7
adverse(adjective, contrary, dreadful, distressing, injurious)
10 years ago|20k views|share |citing 
APASmart Define. (2016). pernicious thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/pernicious/thesaurus/synonyms
ChicagoSmart Define. 2016. "pernicious thesaurus" https://smartdefine.org/pernicious/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2016, pernicious thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/pernicious/thesaurus/synonyms>.
MLASmart Define. "pernicious thesaurus" 24 March 2016. Web. 25 September 2026. <https://smartdefine.org/pernicious/thesaurus/synonyms>