Pernicious is stronger than injurious; that which is injurious is capable of doing harm; that which is pernicious is likely to be destructive. noceo, hurt) is a stronger word than noisome, as referring to that which is injurious or destructive.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

harmful There's no denying the harmful effects of smoking.
detrimental It's not detrimental, but not beneficial either.
hurtful The consequences of cheating are extremely hurtful.
deleterious Insufficient illumination is deleterious to ocular health.
defamatory Amber Heard didn't even name Johnny Depp in the supposedly defamatory comments.
slanderous I never want to hear that slanderous shit again!

Popularity over time

Word	1850 → 2019	Trend
injurious		falling
harmful		steady
detrimental		steady
hurtful		rising
deleterious		falling
defamatory		steady

Use in printed books, per decade from 1850 to 2019.

By length

3 letters: bad¹
4 letters: evil²
5 letters: wrong¹
6 letters: deadly², malign², nocent, inimic
7 letters: harmful², adverse², abusive³, hurtful², noxious², ruinous³, baleful², noisome, baneful
8 letters: damaging³, libelous³
9 letters: invidious⁴, libellous
10 letters: derogatory⁵, pernicious³, defamatory⁵, slanderous³, iniquitous
11 letters: destructive³, detrimental⁴, unfavorable⁵, deleterious⁵, prejudicial⁴
12 letters: unfavourable
15 letters: disadvantageous⁵

The small number after each word is its number of syllables (evil² = 2 syllables).