4
unfavourable
4
vile(adjective, negative emotions)
3
awful(adjective, mean, nasty, offensive, foul)
3
bad to the bone
3
base
3
cataclysmic(adjective, dreadful, harmful, injurious, damaging)
3
counterproductive
3
deathly
3
disserviceable
3
dreadful
3
hateful(adjective, mean, bad, evil, nasty)
3
iniquitous(adjective, bad, corrupt, immoral, distressing)
3
internecine(adjective, violent, cruel, harmful, injurious)
3
maleficent(adjective, bad, hurtful)
3
mephitic
3
nasty(adjective, mean, evil, cruel, wicked)
3
rotten
3
sinful(adjective, bad, evil, nasty, harsh)
3
spiteful(adjective, mean, bad, evil, nasty)
3
terrible
10 years ago|20k views|share |citing 
APASmart Define. (2016). pernicious thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/pernicious/thesaurus/synonyms
ChicagoSmart Define. 2016. "pernicious thesaurus" https://smartdefine.org/pernicious/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2016, pernicious thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/pernicious/thesaurus/synonyms>.
MLASmart Define. "pernicious thesaurus" 24 March 2016. Web. 24 September 2026. <https://smartdefine.org/pernicious/thesaurus/synonyms>