do you think rainford was right to kill zaroff at the end of the story?

Rainsford has gained a certain understanding of what it is like to be hunted, a concept he did not have any idea about early in the story. I think that in the "animalistic" world of hunting and hunted that these men exist in, the killing is the appropriate and indeed expected response for the person who wins. Certainly Zaroff would have killed Rainsford.