1. Ginny Weasley
Even though I like Hermione, Luna, and Fleur better than Ginny but I think Ginny isn't as bad as what people say. Ginny is still a well done character to me, but I always notice on how much people (especially Harry Potter fans) hate Ginny Weasley. Many people hate Ginny Weasley because of her relationship with Harry, being a "Mary Sue," she is a "$!ut", Harry should end up with Draco or Hermione or Luna instead of Ginny, and she is not as pretty as Hermione or Luna or Fleur. I personally think the hate towards Ginny is pretty undeserving.
No matter how much people hate Ginny Weasley, I actually like her relationship with Harry at the sixth book of the Harry Potter (I like their relationship better on the book rather than the movie to be honest, because their relationship on the book is better developed). Some people think her relationship with Harry is the "copy-cat" of James and Lily, it is the contrary I think.
Ginny is not a weak character, yes she is rather weak at the second book but she gets stronger eventually. She gets stronger at the fifth book where she can be useful for Harry to be in the Dumbledore Army. Then on the seventh book, during the "Second Battle of Hogwarts" she is the few people along with Neville and Luna who restored the Dumbledore Army to fight Voldemort and his "death eaters."
As for Ginny being a Mary Sue, I don't think she is one, yes she pretty, witty, spunky, and all that but she doesn't feel like a Mary Sue to me. She has few of her flaws such as not as good as Hermione on casting spells, easily gets jealous, and can be rather clingy. And besides most of the descriptions about Ginny's positive aspects on the books are explained from Harry's point of view, because of how much Harry was in love with Ginny, which is still understandable to me.
2. Usagi Tsukino
She is not exactly my most favorite Sailor Moon character (my most favorites are Minako Aino, Ami Mizuno, and Makoto Kino), but I sometimes feel like the hatred towards her can be really undeserving. Majority of the reasons of why many people hate her is because she is annoying, stupid, whinny, lazy, crybaby, eat too much, being a "Mary Sue," and too clumsy. I do agree that Usagi can be a bit annoying, but at least she isn't that bad, in fact her flaws can be pretty hilarious to watch. Despite of her flaws, she can be a good fighter who puts her heart and soul as a Sailor Moon.
In fact, in the manga I think her character is better developed and more well rounded rather than the anime, which is another reason why I prefer the manga version of the Sailor Moon rather than the anime.
Also, Usagi still can take her responsibility as Sailor Moon quite well even though she can be prone to lose her fighting spirit or being rather fragile. And I also like on the way she is always being so grateful towards the others who has done many things to her.
I noticed that they are a lot many people hate her because of how annoying, clingy, bratty, loud, disrespectful, and rude she is. While I do agree that Chibiusa can be annoying, but she also can be a sweetie for a few times. Actually the whole annoying, clingy, bratty, loud, disrespectful, and rude Chibiusa is better described for the anime version of Chibiusa, manga version of Chibiusa actually isn't really like that.
I honestly like the manga version of her because she has sweeter personality and somewhat more respectful towards Usagi. And besides, her annoying and bratty personality on the anime can be rather funny to watch for a few times to me.
4. Amu Hinamori
I know that the hatred targeted towards Amu isn't as many as the hatred targeted towards the previous three characters that I mentioned above, but I still notice there are quite numerous people who hate Amu so badly. Many people hate Amu because she is a "Mary Sue," insecure about herself, annoying, "preppy," and silly. I actually don't think Amu is that bad, because I quite like her character (even though I like Nadeshiko and Ikuto more than Amu).
Unlike some of the mahou shoujo characters who can be considered to be whiny or crybaby, Amu is in fact not really a crybaby or a whiner. As being insecure about herself, that's only the beginning, but after the series progressed she gets better eventually.
As for being a "Mary Sue" I don't think she is a "Mary Sue," in fact her insecurity about herself is one of her most noticeable flaws along with few others such as scared of ghost and rather dense about Tadase and Ikuto. Those are the flaws I have mentioned that can avoid Amu to be considered as a "Mary Sue" to me.
5. Sakura Kinomoto
I notice the hatred towards her is the fewest among the others that I have mentioned above, but I just feel kind of sad to see the some of the people who hate her with a passion. Comments that broke my heart the most about her are: "she is annoying and should just die in the anime," "Li should just hook up with Meilin or Eriol or Tomoyo," "she is worst anime protagonist to be ever existed."
I like Sakura very much as much as I like Tomoyo, Syaoran, Kero, and the other characters on the Cardcaptor Sakura series. Some people even don't want to explain much about why they hate her, which can be rather confusing to me to find the reason behind their hatred towards her. Then again, there a few people who dislike her because Sakura is a "Mary Sue" or too perfect.
Okay, I do admit that her dense and naive traits can be a bit irritating, but it isn't that bad to me, I still think her dense and naive traits can be cute. Despite the fact the fact that she is naive and dense, but I love her really sweet and caring personality, she is a really friendly cheerful girl with a positive view about almost everything. Also, she is not really as crybaby or as whiny as some of the other mahou shoujo characters, which is good.
As for being a "Mary Sue" or "too perfect," no I don't think so, in fact she has few flaws such as being scared of ghost, being dense about other people's feelings, being naive, doubtful of herself sometimes, easily gets angry when someone teases her, and rather clumsy.
She is not as sophisticated, gentle, matured, or as intelligent as Tomoyo but at least Sakura is athletic, active, and she still did a relatively good job when handling clow cards. I sometimes hate it a bit when some people compare her to Tomoyo by saying that Tomoyo is good while Sakura isn't as good as her. To be honest I mostly don't really like to see some people compare Sakura to Tomoyo because I love both Sakura and Tomoyo very much regardless of their personality.
Then what's even worse, she is listed as one of the "most hated anime heroine" by the Biglobe poll (Biglobe is a Japanese website about anime/manga). Sakura listed as the #16 "most hated anime heroine" which is really undeserving if you ask me, Sakura doesn't deserve to be listed as the #16 "the most hated anime heroine" because I have seen other anime heroines who are worse than her (e.g : Miaka Yuki, Mikuru Asahina, Orihime Inoue, etc.). Thankfully, Sakura is still listed as #1 best "elementary grade student anime character" and #6 best "anime characters named 'Sakura'" by the Biglobe poll.
Plus, I support Sakura's relationship with Syaoran.