Rainsford is the protagonist of the story, and serves the role of both hero and underdog; he is the person intended to receive sympathy from the reader, and he is vastly outgunned by General Zaroff. As a character, he is simply drawn; the story has a "cold open," with no information about Rainsford beyond what can be gleaned from the conversation. When he meets Zaroff, it is revealed that Rainsford is not only a very famous big-game hunter, but the author of a popular book on hunting.
Desperately he struck out with strong strokes after the receding lights of the yacht, but he stopped before he had swum fifty feet. A certain coolheadedness had come to him; it was not the first time he had been in a tight place.
(Connell, "The Most Dangerous Game," classicshorts.com)
Rainsford is determined and self-sufficient; even when thrown from his boat in the middle of the ocean in pitch-black night. His determination serves him well later, as he refuses to give up, even when all his traps fail to kill Zaroff. He seems to be a moral person, holding human life higher than animal life, but is also willing to kill to preserve his own life. In essence, he is the polar opposite of General Zaroff, who kills humans for pleasure; Rainsford has a personal moral code, which he is forced to break for his own survival.