What is the noun form of unscrupulous?

There isn't a direct noun form of "unscrupulous." It's an adjective meaning "having or showing no moral principles; not honest or fair."

However, you can use these words to convey a similar meaning:

General terms:

* Dishonesty

* Lack of ethics

* Moral turpitude

* Immorality

* Lack of integrity

More specific terms:

* Fraud (if referring to deception)

* Corruption (if referring to abuse of power)

* Greed (if referring to excessive desire for wealth)

The best choice will depend on the specific context you are using it in.