Iniquitous means grossly unfair and wicked. An iniquitous system.
It carries a moral charge that unfair does not, which is why it belongs to preaching and to politics. Iniquitous is used of arrangements and laws rather than of people.
1adjectiveiniquitousGrossly unfair and wicked.
“The whole iniquitous arrangement lasted for eighty years.”
iniquitous is a quality.
Iniquity plus -ous, from Latin iniquus, unequal, from in plus aequus, fair.
From iniquity + ous.
Etymology from Wiktionary, CC BY-SA