The conflict that Rainsford goes through in “The Most Dangerous Game” would lead one to think at the end of the story he has seen what it felt like to be hunted. Like Zaroff, he was a skilled hunter too, and he had always felt superior to his prey. However, being on the other side of the hunt, Rainsford came to see what it was like to be tracked down like an animal, and he now understands and feels all the horror and helplessness that the hunted feels.
However, once Rainsford gains the advantage and is able to kill Zaroff, all the lessons he previously learned are forgotten, and he reverts back to the hunter mentality again. He feels no remorse at killing Zaroof, and once again he has become the superior hunter. The relief he initially felt has now turned to pleasure.
This is really a question about how *you* read the story. I say this because the story itself does not come right out and tell us which thing Rainsford feels. You have to decide for yourself what is most likely.
If I had to decide this for myself, I would look at a few key passages and decide what I thought they meant. First, Rainsford keeps telling himself "I must not lose my nerve" or words to that effect while he is being hunted. He feels sick and numb and talks hoarsely through tight teeth. The second passage I would look at is the last: "He had never slept in a better bed, Rainsford decided."
So what do those tell you about how Rainsford feels? The questions is really as much about you and your attitudes as it is about anything that's really in the story.
After killing Zaroff, Rainsford has changed into another " Zaroff ", since successfully killing his quarry, Rainsford enjoyed sleeping in his opponent's bed. Since both, Zaroff and Rainsford are skilled hunters they always felt superior to their prey, and the moment that Rainsford was hiding behind the curtains he felt relief. But after killing his prey, the "beast at bay"'s feel of relief turned into pleasure.