Answer:
-sinful
-forbidden
Step-by-step explanation:
-sinful refers to something that is immoral or wrong.
-forbidden refers to something that you are not allowed to do.
-unnatural refers to something that doesn't follow the normal process of an event.
-violent refers to the use of force to cause harm or damage.
According to this, the word unlawful most likely means sinful and forbidden as it refers in the sentence to something illegal or that it is not allowed.