Iniquitous (adjective)

1. Unjust or wicked.
2. Morally wrong or evil.

Origin:

Late middle english: from latin iniquitās, from iniquus 'unequal, unjust', based on aequus 'equal'. the current sense of the word dates from the late 16th century.

Examples:

1. Iniquitous behavior is never acceptable.
2. The iniquitous act of theft is a crime.
3. An iniquitous ruler will always be hated by their people.
4. The iniquitous nature of the system was revealed in the findings.
5. The iniquitous deal was struck in secret.