"Ender's Teacher"

At battle school, Ender spends his time with Graff, or alone, working on the simulator. He starts out small, but then soon moves up to commanding a fleet. After a year, Mazer Rackham introduces himself to Ender, by attacking him, and explains that he's Ender's teacher as well as his enemy. Under training from Rackham, Ender learns that all the buggers think like a single organism, with the "command center" coming from the queen bugger, since Rackham defeated the buggers the last time from destroying the queen. Ender learns from Rackham that this is an advantage, because people can carry out more strategies at once than the buggers, since they have independent thoughts. Ender is moved to another simulator, where he commands an entire fleet, consisting of some of his best classmates from battle school. He thinks he's battling against simulations under Rackham's strategies, but in the "final exam" in command school, he finds out he was really battling the buggers, after destroying the nearby planet, wiping out a bugger army that extremely outnumbered his fleet. The adults in the room cheer, and thank Ender, telling him that he was the fleet commander of the third invasion and that he destroyed the whole bugger race. Ender becomes angry because Graff and Rackham were using him, and that he destroyed all the buggers without even knowing it. Ender sleeps five days, and when he wakes, his friends tell him that he missed out on the war on Earth and the Locke Proposal, from Peter, to end it. 

While reading, I saw that Ender was heartbroken when he found out he destroyed all the buggers, showing that he's the only person in the story who shows compassion towards them, as well as any sentient beings. He felt betrayed, and completely manipulated, but there wouldn't have been any other way to save the world, since Ender wouldn't have agreed to it. Throughout the novel, the games affect Ender's life, which show that our actions, no matter what our intentions are, have a meaning, and that games don't exist in reality. Ender finds a way around the rules in the games, so he can win, and he ends up hating the game itself. He cares about other people, and wants to be peaceful, but the games he has to win force him to go against being peaceful. If Ender was to have a choice, he'd find a peaceful way, although it might be longer and more difficult, through the games, but since he didn't have a choice, he hates the games that he plays, which mirrors how real life is for most people.