The only thing that General Zaroff is afraid of is boredom.
General Zaroff admits that he is a bit savage. After all, he is a Cossak. Zaroff has decided to make his home on Ship-trap Island and stock it with sailors and imported men he can use as hunting prey.
"Oh," said the general, "it supplies me with the most exciting hunting in the world. No other hunting compares with it for an instant. Every day I hunt, and I never grow bored now, for I have a quarry with which I can match my wits."
The problem is that ordinary animals cannot keep Zaroff’s interest anymore. He is too skilled a hunter to be challenged by a jaguar or elephant. He apparently hates being bored. He calls it his “complaint” and refers to it as “ennui” and boredom. He craves excitement like a drug. He thinks Rainsford is his ticket to exhilaration. In the end, Rainsford does cause him a challenge, because Rainsford wins. When he finds Rasinford in his room, he is excited and describes it as “splendid” that they will fight—but Rainsdford wins.