General Zaroff is classist and racist.
A racist is a person who considers those of other races inferior. Zaroff is a racist because he considers people of other races fodder for hunting. A classist is a person who considers people of other classes inferior. General Zarroff is also a classist because he thinks it is okay to kill poor people, especially sailors. He feels that they are less valuable than others.
General Zaroff definitely considers himself superior to just about everyone else. He is rich, and he is smart. As far as he is concerned, that gives him godlike rights over others. If he catches you, he can kill you.
When Rainsford lands on Zaroff’s island, he is surprised to find out that others have been trapped there before. Zaroff repeatedly captures sailors to use as bait for hunting. Zaroff explains to Rainsford that he is strong, and they are weak.
“… If I wish to hunt, why should I not? I hunt the scum of the earth: sailors from tramp ships--lassars, blacks, Chinese, whites, mongrels--a thoroughbred horse or hound is worth more than a score of them."
His answer definitely appears racist, and it would be easy to dismiss him as such. However, he also has no qualms about killing Rainsford, who is white. Zaroff does not mind killing anyone he has in his clutches.
Race is important to Zaroff. He introduces himself to Rainsford by race.
"Oh, you can trust me," said the Cossack. "I will give you my word as a gentleman and a sportsman. Of course you, in turn, must agree to say nothing of your visit here."
I guess you could say that Zaroff is a killer. He seems to kill indiscriminately. He collects and kills sailors, but he also has no problem killing Rainsford. He is a terrible person and a psychopath.