Ender is a monster because he killed the bugger planet without completely understanding them. He also killed other kids unknowingly but still should’ve stopped fighting them once they were on the ground. Ender should have listened to his voice inside that told him to stop fighting his opponent once they are in the ground. A six year old should not be killing other six year olds.
One reason why Ender is a monster because he killed one of his piers, Stilson. After Peter stops Ender from breathing, “Ender stood there watching him laugh and thought of Stilson, thought of how it felt to crunch into his body. This is who needed it. This is who should have got it” (14). Even after Ender kills Stilson, he is still considering getting into a fight again,