At the beginning of the story, Zaroff treats Rainsford with honor and respect. When the two characters first meet, Zaroff knows that he is in the presence of another great hunter. Zaroff is honored to host Rainsford, and Zaroff would very much like to have Rainsford accompany him on a hunt. I believe at this point in the story Zaroff is hoping that Rainsford will be a fellow hunting buddy.
"We will have some capital hunting, you and I," said the general. "I shall be most glad to have your society."
Rainsford is adamant that he will not hunt another human being. He even goes so far as to demand release from the island.
"General," said Rainsford firmly, "I wish to leave this island at once."
It's at that moment that Zaroff's treatment of Rainsford changes.
"I wish to go today," said Rainsford. He saw the dead black eyes of the general on him, studying him. General Zaroff's face suddenly brightened.
Zaroff no longer treats Rainsford like a potential hunting partner. Instead, Zaroff treats Rainsford like any other potential human prey of his. Zaroff knows that Rainsford is in good health. Zaroff gives Rainsford a knife, and Zaroff gives Rainsford the same three-day deal that he gives the other victims.
I don't believe Zaroff in any way changes his treatment of Rainsford during the story. Although Zaroff graciously wines and dines Rainsford before revealing his true intentions, Zaroff continues to treat Rainsford honorably, adhering to his own rules of the game without breaking them. Zaroff promises that Rainsford can have his freedom if Rainsford eludes him during the time that is established, and Zaroff keeps his word. When Zaroff returns to his home, he knows that he has lost the game, and there is no inclination that he will look for Rainsford further. Later, when they meet again, he tells Rainsford that "You have won the game." When Rainsford announces that a new game will begin, Zaroff accepts the terms.
In the first moments when the two meet it seems that Zaroff has respect for Rainsford as he has read his books on hunting. Then it is revealed that he actually is looking forward to challenging Rainsfords skills as a hunter. Then at the end when Zaroff is defeated by Rainsford his demeanor goes to one of respect again. It is very evident in the story that Zaroff feels he is the top hunter and that he can not be out done but Rainsford shows him different by eluding him for an ample period of time to show him that he is not the top hunter after all.