How are Peter and Valentine different from each other?
While Peter and Valentine work together to manipulate global politics, they are very different characters, serving as foils for each other and for Ender. While Peter is defined by his abusive and sadistic tendencies, Valentine is defined by her compassion. Both are rejected as candidates for battle school, but for opposite reasons. Ender is positioned, generally speaking, as a midpoint between the two of them.
Both Peter and Valentine are framed as being out of balance, at least by the standards of the battle school. We can wonder whether Valentine would have been manipulated in the same way as Ender and helped participate in a genocidal war, or whether Peter would have felt any regret at the act. Ender, ultimately, is a more complex and thus more interesting character, and Peter and Valentine largely serve to bring out the different sides of Ender.
check Approved by eNotes Editorial