General Zaroff is educated and cultivated, but has no sense of morality.
There are many different ways to characterize. Generally, we divide characterization into the categories of direct and indirect. Direct characterization is when the narrator describes someone. Indirect characterization is what we learn about a character from what he says and does.
An example of the two types of characterization can be seen in this paragraph.
In a cultivated voice marked by a slight accent that gave it added precision and deliberateness, he said, "It is a very great pleasure and honor to welcome Mr. Sanger Rainsford, the celebrated hunter, to my home."
The fact that he is precise and deliberate is editorial by Rainsford, the narrator. This is direct characterization. The fact that he knew who Rainsford was shows that he is both a hunter and an educated man. He is well-read enough to have read many books on hunting, including those by Rainsford.