Professor Neville Longbottom (b. 30 July, 1980) was a pure-blood wizard who began school at Hogwarts School of Witchcraft and Wizardry in 1991, and was sorted into Gryffindor house. His parents, Alice and Frank Longbottom, were well-respected Aurors and members of the first Order of the Phoenix. Shortly after Neville's birth, they were tortured to insanity by four Death Eaters with the Cruciatus Curse and placed in the Janus Thickey Ward at St Mungo's Hospital for Magical Maladies and Injuries, leaving Neville to be raised by his formidable grandmother, Augusta Longbottom.
Coming to attend Hogwarts, Neville quickly developed a reputation as being an incompetent and accident-prone dolt. Harry Potter only learned the truth about him near the end of his first year. However, Neville's having the courage to stand up to his own friends impressed Dumbledore so much that he awarded just enough house points to him to allow Gryffindor to win the House Cup.
Neville would go on to be a part of Dumbledore's Army, where he came face-to-face with Bellastrix Lestrange, the Death Eater who tortured his parents to insanity. When Voldemort's Death Eaters took over Hogwarts, Neville led the resistance against them, even suffering torture from the Death Eaters in response to his defiance. During the final battle he proved himself to be a true Gryffindor by wielding Godric Gryffindor's sword and using it to slay Nagini, Voldemort's final Horcrux, itself an act that sealed the Dark Lord's fate, because of this, it could be implied that he was the one that ended up killing the Dark Lord.