> that demonstrates that with the right environment, even the most intelligent can be taught to use their skills in an utilitarian and amoral way - the book ends with Ender becoming the worst mass murderer in the history of the human race, despite representing the moral middle ground between his monstrous brother and his saintly sister.

Uh, I remember it as Ender having been tricked into it. He thought he was still doing simulations to prove his tactical ability, with how the scenarios kept getting more difficult, and did things he never would have done if he knew it was real.