Cedric Diggory was obviously set up as a hero type from the beginning. He's handsome, kind, hardworking, honest, athletic and noble. A classic hero in every respect - which should make him instantly hated by everyone except that he doesn't seem to know or care. This is just how he is. So it's a double shame that his fate was simply that of an unwanted "spare." In a different universe, he'd have been Head Boy in his final year at Hogwart's.
Lily Potter. Harry's mother. We know less about her than we know of James. We don't know her maiden name. We don't know if she played Quidditch or any other sports. We don't know who her friends were - who did she hang out with when she wasn't with James? All we know is that she was brave and loving, good with charms and came from a Muggle family that made so much of her that her sister hated her. And her son has her eyes. Whereas, we know James' sport, James' best friends, and that he as...cavalier about rules as his son. And other than his eyes, his son looks like him. We also know he comes of a wizarding family, but we know *nothing* of the family. In fact, it seems there are no other members of it left, other than Harry himself. Obviously, if there were, Harry would not have been given to the Dursley's, or at least they would have contacted him at Hogwarts by now.
I'm also dying to know more about Snape. He's a wonderfully complex character - he seems so evil, but Dumbledore trusts him implicitly, and he has made a great deal of threats that he's never carried out - and in turning against the Death Eaters and then spying for them, he's done an amazingly brave act that adds even more depth to his character.
On the other hand, I also believe that Snape had a huge crush on James Potter (much like some folk believe Malfoy has now) and that it was not only unanswered because James was in love with Lily, but it's also possible that, cruel as boys are, he and his cronies, including the possible lovers Sirius and Remus, made fun of him for it when he actually admitted it.
That's a good enough reason for an abiding hate. And now, here's Harry. And he looks like James except he has Lily's eyes....