At the beginning of the story, Rainsford is an avid hunter, feeling man is superior to animals, that his prey has no feelings, and that hunting in general is just a game. He thinks that the world is divided between the hunter and the hunted. This opinion changes when he learns Zaroff intends to use him as prey, however. Once Rainsford accepts that he must participate in Zaroff's "game", Rainsford becomes much like Zaroff. He becomes a killer when he kills Zaroff's dog and then Ivan. By the end of the story, Rainsford kills Zaroff, and we don't know if he has become like Zaroff.
Zaroff has a similar opinion regarding his prey. Big-game hunting has become boring for Zaroff because the animals can't use logic, so they offer no challenge. As a result, Zaroff imprisons sailors that he calls the "scum of the earth" and has them become as physically fit as possible. Zaroff wants his prey to offer him as big a challenge as they possibly can. Zaroff sees the world divided between the strong and the weak. His prey, the captured sailors from ships he's trapped on his island, have no rights because they are the weak. They have no rights and no feelings. Zaroff is really excited when he realizes he has a real challenge in Rainsford, who has quite a reputation for hunting. In the end, Rainsford proves to be more cunning than Zaroff, and Zaroff pays the ultimate price--his death.