If you think of techniques an author uses to delineate a character so that the reader understands the character, Orson Scott Card uses many ideas. Ender Wiggin is first introduced as a bullied 6 year old who loves his sister Valentine and essentially hates his psychopath brother, Peter. When Ender is on the transport ship, he is set up by the commanders to be bullied and isolated. Ender responds by enduring and then finally attacking the persecutors. Any student who has been bullied can understand Ender's frustration. When Ender gets to Battle School, he is one of the youngest and must learn quickly. The author makes the reader look at Ender as a bullied youngster and yet as someone who might kill as he did on the transport. So Ender has empathy for those who get bullied as he does, but he can also be ruthless as he is with Bonzo's followers. Ender's speech can also reveal his character. He tells Valentine about understanding his enemies, "In that very moment when I love them, ... I destroy them." So the author uses other people's descriptions or actions with Ender, Ender's response, Ender's empathy for others, his speech describing his actions and feelings, and even Ender's brilliance as a commander, for no one else at the Battle School has the imagination to defeat him. Though he is a complex character, Ender is a mostly sympathetic character in a fascinating book.