Strong, direct, and negative:
* Iniquitous: emphasizing extreme wickedness or injustice
* Abominable: expressing disgust and revulsion
* Depraved: highlighting moral corruption and perversion
* Vile: emphasizing extreme baseness and worthlessness
* Heinous: emphasizing extreme cruelty and brutality
* Nefarious: suggesting evil and criminal intent
* Diabolical: implying a connection to the devil or evil spirits
More subtle or nuanced:
* Immoral: focusing on a violation of moral principles
* Unholy: emphasizing a lack of spiritual purity
* Corrupt: emphasizing a deviation from integrity and honesty
* Transgressive: highlighting a violation of rules or boundaries
* Unrighteous: suggesting a lack of justice or fairness
* Wicked: a common term for evil or immoral behavior
* Sinful: specifically referring to a violation of religious or moral laws
Figurative or metaphorical:
* Dark: suggesting something sinister or evil
* Unnatural: implying something unnatural or monstrous
* Twisted: suggesting something distorted or perverse
* Blighted: implying something ruined or corrupted
The best word to use will depend on the specific context and the desired effect.