Ender's fight with Bonzo mirrors his fight with Stilson. In both cases Ender ends up hurting someone when all he wants to do is to protect himself from being hurt in the future. Ender kills both boys, yet he is not the aggressor in either case. The main difference between the two fights is that Stilson likely would not have killed Ender. He was just a bully who picked a fight with the wrong kid. Bonzo wanted blood, and Ender knew he needed to defend himself. Ender's fight with Bonzo also cost him more. He did not want to hurt anyone and he is sure that he did terrible damage to his opponent. It shows him that he cannot escape hurting people. In fact, his life is now made up of a pattern of hurting people who have become his enemies. But, unlike everyone around him, Ender does not think that Bonzo had it coming—he simply wishes that Bonzo would have left him alone so no one would have been hurt. Ender is still filled with compassion, but he now seems to have no place for it in his life.
Immediately after the Bonzo fight, the worst event in Ender's life so far, he is forced to fight a battle with impossible odds. Graff pushes Ender to the limits of human endurance, and Ender succeeds, but he no longer cares about winning. In fact, he no longer cares much at all. All Ender knows is that the same adults who care so much about him winning his games let a fight take place in which Bonzo was seriously injured and he was forced to hurt him. Earlier Ender hated the teachers and saw them as the enemy, but now he does not wish to have any enemy at all. He does not want to play any games at all. Ender leaves the Battle School with no belongings, just as he came. He still has some humanity left, but the despair and apathy that gripped him once before have again taken hold of him. Ender Wiggin survived Battle School, but it is uncertain how much of him will be left when he gets to Command School.