I think my favorite thing written to evaluate the latter books of the Harry Potter series are on enembee's profile page:
"The ultimate problem was that the first few books imply that the overall story would be about a boy growing up to be a hero, and what we ultimately got was the story about a patsy who was manipulated into fulfilling someone else's overly complicated scheme to preserve the status quo of a society that didn't deserve salvation"
Although I love the series overall, Harry doesn't become a hero under his own power, and nobody else really becomes a hero, either. You could count Snape, who is one of my favorite characters, but in the end he doesn't live up to the potential and power JKR gives him early. Seriously, he could have at least put up a fight! Dumbledore resists the hero persona because he's old, he's manipulative, and he has lots of skeletons in the closet. Hermione and Ron aren't independent enough, disregarding the fact that Ron just doesn't do that much heroic stuff. Everybody else is too minor of a character to be the story's hero, so we're left with a weak antagonist who succeeds almost in spite of his own efforts. I think that's one of the biggest reasons that Harry Potter fanfiction is so huge. Everybody wants to fix either the characters or the story to fulfill the need for a strong hero.
My thoughts on characters:
-Ginny: Although OoTP shows that Ginny has magical potential, and CoS puts her in some trying situations, she also succumbs to the weak heroine disease. Her character isn't explored enough to make her interesting, and I find it disappointing that her character's potential to become an active part of the story is sidelined so she can be Harry's love interest. I like stories where she becomes independent and self-sufficient, and I think she and Neville make a great match.
-Ron: Ron is often used in fanfiction as either an undyingly loyal friend or as a judgmental jerk (like in most Slytherin-Harry stories). No one can deny that, in the books, he's always stubborn. But that doesn't mean he can't either make mistakes or refrain from making mistakes. I enjoy reading fics where his stubbornness is not his only personality trait, where he contributes something, where he is not totally obsessed with Quidditch, and where his only talent isn't chess.
-Hermione: Her intelligence is a useful plot device, but doesn't leave much room for her own development. I think she's much more believable than many of the other main characters, however, and so she's a good candidate for many different topics in fanfiction. I also think that her pairing with Ron is ludicrous as portrayed in the books, as I see their fighting as more familial, regardless of Ron's jealousy (which I don't think reflects his character very well). I think that Hermione and Draco make a much better match, pending Draco's turn to the light side...
-Draco and the Malfoys: I think that the Malfoys were portrayed well in canon, but there isn't enough information about them to be restrictive in fanficdom. I particularly like the idea that they are secretly anti-Voldemort, perhaps coerced into helping him by the older generation, and I think that Lucius' name (meaning light) shows that JKR might have planned to have them turn more light at the beginning. Obviously Draco would have to get over his preconceived ideas, but I think that he has the potential. I dislike stories that show him just suddenly deciding to turn good because he's fallen in love with Hermione, or ones that say he's been pretending to be dark all along. There's no way an eleven-year-old could cultivate that kind of rivalry with Harry as a pretense.
-Luna: I really, really like the idea that Luna is actually a rational person and is just hiding herself under all the fluff she uses. Yes, she is uniquely insightful as is, but I think that she could just be very clever and say strange things, while understanding more underneath. This would have to be part of her character since, as I noted above, I don't think that an eleven-year-old could pull off a great cover, but I could see her being weird upon coming to Hogwarts, and then acting the same way to protect herself from unkind peers, rather than trusting them to accept her as she came to understand more things about the world.
-Neville: He is so great. He really isn't developed much in canon, but I love how fanfic stories are able to show his strength, loyalty, and compassion. Those are also demonstrated in the books, but he really doesn't do much with them that we can see. Strong Neville stories are awesome.
-Snape: Oh, Snape. He's such a flexible character for fanfic. I think he's the most complex person in canon. I dislike fics that say he could have ended up with Lily, as I just don't see that relationship working, but most other Snape-centric fics are great. However, I think he's a fine character as he is, and although his attitude can soften over time, it really doesn't make sense to have him just suddenly become a cuddly, nice kind of person. He doesn't have to be nice to be good, people! I like stories that have him as Harry's guardian and, occasionally, as Harry's dad (you'd better have a darn good explanation for how that happened, or else a darn good reason for why Harry has to have him as his father for the story). Some Snape-Hermione fics work out, but as time passes I'm seeing more and more of them as creepy.
-Dumbledore: Oh boy, another complex character. I like that about him, but whereas Snape is usually seen as a good guy in fanfic, Dumbledore can go either way. I personally am more of a Dumble-hater. Although he does lots of great things, his manipulations hurt people, and I tend to disagree with his "the ends justify the means" theory. I really like independent Harry stories, and Dumbledore makes a great gray villain in those stories. He's not unendingly evil, but he is an opponent who needs to be escaped from.
That's all, folks! I will add more character analyses as time and motivation permit.
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