The moment that zaroff decides rains ford will not be a hunting partner, but a huntee is very clear write down two sentences that show the general making his decision

Answer : The lines when they were leaving the island, Zaroff rebuffs request f Rainsford and says, "You've only just come. You've had no hunting--"

Then Rainsford replied by shooking his head. "No general ... I will not hunt"

These were the two sentences that clearly shows that Zaroff already decided that Rainsford will not be his hunting partner but rather a huntee.