Does Rainsford really kill Zaroff in "The Most Dangerous Game"? I thought he just let him go.

Yes, Rainsford did really kill General Zaroff. In the story, it says, "The general made one of his deepest bows. 'I see,' he said. "Splendid! One of us is to furnish a repast for the hounds. The other will sleep in this excellent bed. On guard, Rainsford....'" From this, we know that the two men are going to fight and that only one man will sleep in the bed and the other will be dog food. Because the next/last line states, "He had never slept in a better bed, Rainsford decided," we know that General Zaroff became dog food.