Rape of Tamar
Although he was the heir-apparent to David's throne, Amnon is best remembered for the rape of his half-sister Tamar, daughter of David with Maachah.
Despite the biblical prohibition on sexual relations between half-brothers and sisters, (Leviticus 18:11) Amnon had an overwhelming desire for her. He took advice from his cousin, Jonadab the son of Shimeah, David's brother, to lure Tamar into his quarters by pretending to be sick and desiring her to cook a special meal for him. While in his quarters, and ignoring her protests, he raped her.
Two years later, to avenge his sister, Absalom, Amnon's half-brother and Tamar's full brother, sent his servants to kill Amnon at a feast where he was drunk to which he had invited all the king's sons. (2 Samuel 13)
Read more about this topic: Amnon