Perverts in general. In response to the fact that There Are No Girls on the Internet, many male players are depicted as flocking to and hitting on the few females there are, which is often presented as annoying and creepy. This is especially prevalent in GGO, which has a lower female playerbase than most, where many of them make a bunch of pervy comments towards female players and one is outright shown leering at Sinon's body while hitting on her. Even Klein, who's one of the main characters and whose perversion is Played for Laughs, often ends up as a Butt-Monkey whose appreciation of women isn't exactly portrayed as a positive characteristic of his. It's even worse with full on rapists, who are, for very good reasons, often Hate Sink characters who end up dismembered messes by the end. The only real exception is Kyouji, and that because he's more of a Jerkass Woobie as opposed to the Complete Monster that Sugou was.
PKers, or to simplify, players who spend most of their time in online games killing other players, are also not portrayed positively. In the first arc, any and all PKers, some of which even starting a guild dedicated to it, are essentially Serial Killers due to the death game nature of Sword Art Online, with many going on to become Big Bads in other arcs like Phantom Bullet and Alicization. Even in later arcs where the games lack life-and-death stakes, PKers are typically shown to take being G.I.F.Ts to great extremes and are even portrayed as outright creeps, such as the Salamander Players led by Kagemune who are heavily implied to be "Women Hunters", players who take advantage of the combat system to avoid setting off the Anti-Harassment code to harass female players and sometimes derive pleasure from killing them.
Accidental Aesop: The Aesop of the Phantom Bullet arc is meant to be a commentary on the dangers of losing yourself in a fictional world, like Kyouji did in Gun Gale Online. It also could be interpreted as a message in favor of letting characters re-allocate their stats, since maybe Kyouji wouldn't have gone off the deep end if he'd been allowed to change his stats around and invest some points into Strength.
In SAO II Episode 8, Kirito finds Sinon in the BoB. She tries to draw her pistol on him, but he immediately pins both her hands down and presses her back against the ledge. Without context, it could easily be misinterpreted as them making out or Kirito assaulting her.
In Alicization Episode 1, a kid Kirito and Eugeo have a tickle fight with each other, but the camera angle is pointed at their rear ends and the excited giggling can be interpreted a lot of ways for those who don't have context.
Adaptation Displacement: There is a very large portion of anime-only fans who are unaware Sword Art Online started as a light novel and may even be under the belief that it has a manga as the source material.
Eugeo. His issues aside, he filled this bill more than Kirito. Not only he is very nice but he's also very shy and adorable, while also being a kind of a geek as well. Oh, and he's also a gigantic Badass Adorable due to his character development as well.
Alice. She's an Integrity Knight with No Social Skills, making for lots of cute moments where she doesn't know how to properly respond in social circumstances.
In Progressive, Asuna has moments of these due to her general inexperience with MMOs. Not only did she use her Real Name as a Username, even using her full name when introducing herself to Argo in the manga, but her curious nature about the game, her joyful reactions to things like baths or sweets, and her Big Sister Worship of Kizmel makes her very much Badass Adorable.
Angst Dissonance: During the Aincrad arc, a lot of players struggled to cope with a truly desperate situation. Later stories feature normal, non-deadly MMOs where the players (mostly Aincrad veterans, but for good reason) are still acting like it's the Vietnam War.
Kirito's Survivor's Guilt seems to disappear at times and he'll be back to his cheery Nice Guy self an episode later. This one is justified though. The Phantom Bullet arc reveals that it's not that Kirito no longer feels the pain and trauma, he's just good at hiding it. But scratch the surface and he's still haunted by the horrors he's seen with lapses that are akin to PTSD, such as his flashbacks of being forced to kill members of Laughing Coffin.
Asuna seems all too eager to head right back into ALOnote technically the version she later plays is New ALO, which isn't the same one featured in the Fairy Dance arc, with lots of the features implemented by Nobuyuki Sugou being removed with her friends, given that she spent months trapped there as the humiliatingprisoner of a sadist. Somewhat justified, since not only is it the game that her SAO friends have decided to gather in, she only truly feels alive and in-control of her life as a skilled swordswoman in the virtual world, rather than as the daughter of an overly-strict mother.
Anti-Climax Boss: Chudelkin. He was built up to be quite a threat with his mastery of the Sacred Arts summoning up a fire golem, but he gets defeated very quickly with Alice blocking his attack and Kirito killing him without breaking a sweat.
The Fairy Dance arc as a whole, which has the opposite problem of the Aincrad arc. While people thought the Aincrad arc was too rushed and could have been extended out longer, everyone just wanted the Fairy Dance arc to be over with and the tedious "rescue Asuna" plot to end. This is especially the case in Episode 21 where there's the perfect opportunity for Asuna to escape and she very nearly does. But nope, it has to continue to be dragged out so that Kirito can have the final showdown with the Big Bad, complete with the squick-inducingAttempted Rape scene.
The Phantom Bullet and Alicization story arc would feature the same problems, especially the latter, whose length forced it to be adapted into anime in three different blocks (originally two before the COVID-19 Pandemic).
The Mother's Rosario arc gives Asuna some independence from Kirito and makes her far less of a Satellite Love Interest, which some had been accusing her of being. After her argument with her mother, she decides not to call Kirito, and while Kirito and Klein buy Asuna and the Sleeping Knights time to get into the boss room, Asuna and Yuuki ultimately play the greatest role in defeating the boss.
The Alicization arc seems to be going out of its way to not make Kirito overpowered to start with and shows him with a lot of fumbling and learning. Kirito is overwhelmed in real life by Johnny Black, who stabs him in the heart with a syringe, and this time there's no Pocket Protector to save him. While in the Underworld, Kirito has trouble landing a proper hit with Eugeo's axe on the Great Cedar tree and has to be taught how to posture himself.After he wakes up from his Angst Coma, any hope of him not being so over powered goes down the drain.
A meta case happened after the infamous episode 10 of Alicization. After the third Attempted Rape scene in the franchise, which was also the most violent and graphic one up to that point, Reki Kawahara went out on Twitter to explain why he used that plot point that many times, the reason being that the light novels he used to read in middle school just used it quite often too for Catharsis Factor effect, and he imitated them. However, since it had been almost a full decade since he wrote Sword Art Online as a web novel, Kawahara stated that he doesn't find that plot device appealing anymore, and vowed to find other ways to give catharsis to the reader.
Midway through Episode 39 of Alicization, a massive force of bloodthirsty American, Chinese, and South Korean players enters Underworld to serve as GDS's reinforcements. This was the most controversial plot point of the light novels, to the point that Kawahara himself admitted in the afterword of Volume 17 that he was very tempted to rewrite this before publication. It was somewhat mitigated thanks to the existence of the Korean player Wol-saeng alias "Moonphase" who had the sense to be suspicious of what was going on but there was no such equivalent for the Chinese faction, who were just a nameless, faceless horde. The anime adaptation specifically created the character of Mei Mei Xiang, who is one of Moonphase's friends and equally as suspicious as him, to give a sympathetic name and face to the Chinese player faction.
Awesome Art: Regardless of the many criticisms the plot and character development get, one thing that has consistently been praised for SAO is how spectacular the animation is:
The many games the series has featured all have very beautifully drawn landscapes, especially SAO.
Kirito vs. the Gleam Eyes. How could one not be awed by this spectacle when seeing Kirito unleash the Starburst Stream? The sheer amount of work put into the animation of the 16/20-hit combo is undeniably epic.
The climactic battle with Death Gun was praised even by haters. Particularly spectacular is when Kirito's SAO avatar gets superimposed over his GGO avatar, when he reaches for his gun to shoot Death Gun.
Alicization in general is full of detailed scenes due to the Art Shift.
While Klein was never the equal of Kirito in SAO, he filled an important role in Aincrad as Kirito's loyal friend and foil, even when Kirito didn't believe that he deserved the friendship; by Excaliber he's degraded to comic relief and the butt of the jokes, and yet he's still crucial to its success. Alleviated somewhat in the Mother's Rosario arc, where he's seen swatting dozens of players out of the way with ease, and in Ordinal Scale, where he and his guild are among some of the only players to hold their own against the first Event Boss while Kirito falls flat on his face and needs bailing out, and may have actually won a fist fight with Eiji had the latter not had an additional AR device to read his opponent's movements.
Asuna got subjected to this post-Aincrad, with her first being reduced to Badass in Distress before becoming a Satellite Love Interest. The Mother's Rosario arc and Ordinal Scale heavily fix these issues, as Asuna shows how competent of a fighter she is on her own without Kirito backing her. Especially prevalent in the movie, where she actually outshines Kirito for a large part of the film, being crowned the MVP for the first two boss battles (when Kirito is struggling) and showing off her exceptional leadership skills in combat. She only takes a back seat after Taking the Bullet for Silica and losing her memory, forcing Kirito to step in when the game stops being a game, but even then she's still able to pull off a Big Damn Heroes against the Final Boss who had been stomping Kirito's party, before showing off the Mother's Rosario OSS she got from Yuuki to finish the boss off.
While he hardly suffers this in the main series, many spin-offs have turned General Eugene from a Worthy Opponent for Kirito and one of the contenders for World's Best Warrior into something of a joke. In materials such as the events in Memory Defrag, he's a frequent victim of the Worf Effect, being shown or stated to be defeated by the Monster of the Week to establish their threat, and in Lost Song he's not only defeated by Sumeragi to establish the latter's power, but Sumeragi also took his Demonic Sword Gram as a prize yet is never shown using it, as if to rub salt on the wound. He finally gets some Character Rerailment in Rising Steel, where he duels Klein, one of SAO's top players, as part of a ploy to get the gathered players to join the War of Underworld, and was on the giving end of a Curb-Stomp Battle before the latter performed a Suicide Attack against him.
Sinon gets hit with this for some in the Calibur arc. Despite being introduced as a badass Cold Sniper who isn't weighed down by having a crush on Kirito, she ends up having a reduced role in the arc where many felt she was just another girl in the harem. Though to her credit, she still pulls off a few badass moments in the arc, such as her 200-meter shot to recover the falling Excalibur.
In spite of her importance to the Arc, Alice ends up suffering from this over the course of the War of Underworld. Despite Fanatio naming her "the Strongest Integrity Knight", and while the Sacred Art she used to vaporize the Dark Territory forces is a testament to her power, Alice since then never enters many encounters that would further prove the status Fanatio thrust upon her. While she certainly retains her skills, and being able to briefly go toe-to-toe with Asuna is noteworthy, she is kidnapped by Vecta almost immediately after and is put to sleep by him for good measure. Even after she awakens up, she never gets into any fights thereafter, immediately rushing to the Worlds End Alter to escape Vecta and, even when he does catch up to her as Subtilizer, they're unable to have a proper confrontation because of Kirito arriving in time and dealing with him personally.
The Official Couple Kirito and Asuna. Two of the most polarizing heroes in The New '10s anime history. On the broad strokes, some claim that both are a little bit too perfect, thus making them unrelatable, if not downright unlikable. Others find them as perfectly engaging protagonists, specially when they are together as a Battle Couple (See Escapist Character below). To be more specific:
For Kirito it mostly has to do with whether or not he is a bland self-insert Wish Fulfillment character as opposed to being a completely legitimate and believably badass lead with a well-formed character. There are a lot of arguments over whether his overpoweredness is justified or completely unreasonable, with detractors stating this simply does not happen in video games and only appeals to those seeking a tasteless power fantasy, while fans point out it's explained In-Universe why he's so strong, such as his tendency to fight solo as opposed to fighting in groups. Detractors also argue that, even leaving aside his "overpoweredness" arguably breaking both the character and the narrative, Kirito's badassery just doesn't work in this setting, as the original appeal of the premise comes from the imminent threat of death, which is negated by him being an Invincible Hero who never has a real risk of dying. His Chick Magnet status and the way the story tends to focus on him instead of on arguably more interesting characters are also huge points of contention. For some, these points make him almost unbearable to watch, to the point that detractors treat him like a Hate Sink character, while others don't mind them and argue they're just blown out of proportion by the detractors, seeing him as a legitimate Escapist Character.
As for Asuna, she is either one of the most moe, badass and likable, strong female leads in The New '10s anime history or another typical and run-of-the-mill tsundere Love Interest. Then there was another group who thought she started off brilliantly as a strong female lead with her own independent character, but her appeal decayed after she became all lovey-dovey towards Kirito and began revolving around him, specially after the Aincrad arc, albeit this last part was alleviated by the Mother's Rosario arc, and the Ordinal Scale movie to a lesser degree. It's not uncommon to find those who hate SAO but still find an appeal in Asuna on her own. The way Kawahara tends to put her in the background in arcs like Phantom Bullet despite being the female lead of the franchise also hurts her reputation among detractors. And of course, there's her role in the Fairy Dance arc. For most detractors it utterly broke her beyond repair. Fans on the other hand, while conceding that Kawahara was just disrespectful to her in that arc in general, argue that there were mitigating factors, namely the fact that she almost gets to escape on her own with no help, and even then she manages to give Kirito the means to get to her, and she never sees herself in that situation ever again. Her pampering background is another point of debate, albeit to a lesser degree (to some people, it gives her more depth; to others, it makes her even less relatable).
Yui is a Tastes Like Diabetes variation. Fans think that she's adorable and contributed to Kirito and Asuna's relationship. Detractors on the other hand see her as a lolicon-pandering bait and a dreaded moeblob who contributed to the show's Seasonal Rot. There's also the fact that she often serves as a walking plot device, pulling out something from nowhere to further advance the story.
Suguha in the Fairy Dance anime adaptation can be either seen as a Deconstruction of Kissing Cousins and Not Blood Siblings or a toxic Little Sister Heroine who repeatedly goes "Kirito-kun" or "Onii-chan" in just about every scene she's in and "steals" the role of the heroine from Asuna. There's also the excessive fanservice that comes with her character, such as the repeated close-ups of her oversized bust. For some, that's an appeal to her character, while for others, it's incredibly annoying pandering to a certain demographic.
Silica. To some, she's one of the most interesting and endearing characters in the whole cast, seeing her as Everyone's Baby Sister. To others, she's a useless character who contributes nothing to the plot other than being a Token Mini-Moe, especially given how she's often The Load and needs to be rescued.
Alice Synthesis Thirty. While the young Alice Zuberg was near universally loved, Integrity Knight Alice has had a more divisive reception from the fanbase. Some love Alice for just how complex her story arc is, how incredibly badass she is being one of the few who can contend with Kirito, and the sheer amount of Character Development she goes through from The StoicLady of War to a more kind-hearted and friendly girl. Then there's those who dislike her pre-development for her rude and brash attitude and post-development for the fact out of all of Kirito's Unwanted Harem she is the only one who actively butts heads with Asuna over Kirito's affection and want her out of the picture for Kirito and Asuna's relationship.
Gabriel, the Big Bad of the War of the Underworld half of Alicization. For some he's a very complex and terrifying Love to Hate villain with a fleshed-out backstory, while for others he's just god-awful scum who needs to hurry up and die. The anime only made this worse with him having rape tendencies added to his character that weren't present in the light novel.
Recon, albeit with his fans and haters generally not being very vocal. There are some fans who like him for his friendship with Leafa, viewed him as a nice alternative to Kirito as Leafa's Love Interest, and just generally found his personality Adorkable. To others however, he comes off as a clingy third-wheel to Leafa, who was already a third-wheel for Kirito/Asuna, and fans tended to be extremely annoyed by Recon's presence and felt he was a pointless character who added next to nothing to the narrative. Him being Put on a Bus was either welcomed or bemoaned by fans.
Big-Lipped Alligator Moment: The Naughty Tentacles scene in Episode 21 that Asuna is subjected to. It comes out of nowhere, adds nothing to the plot, is never mentioned again, and just seems to be done for the sake of invoking the All Anime Is Naughty Tentacles theme. Similarly, the fact that two ALO staff members go around in purple slug avatars for no real reason is discontinued and bizarre enough for it to count as another BLAM.
Bile Fascination: There's a fair number of late-coming viewers that jumped in after it became a critic-favorite punching bag in the anime community. In fact, SAO became a "must watch" among the anime community so that viewers can see why it's terrible and allow them to be able to join in the bashing of it.
The use of sexual assault in the series, especially the borderline graphic attempted rape in Alicization, has split fans on whether or not seeing the rapists taken out is catharsis due to Rape Is a Special Kind of Evil, or just a cheap shot at it reducing the female characters to damsels for the males to rescue.
Also, the increased instance of gore and violence in Alicization, which is divided between those that consider the creators increasing shock value for whatever reason and those who insist that it is necessary to depict the plight and pains of the protagonists (not to mention its depiction aren't too consistent as some characters Disappears into Light as usual while some are bloodied and gored)
Whether the anime adaptation is a step down from the light novels, or just as good/bad as the source material. Many light novel fans who followed the series before the hype and its reputation got destroyed state the anime Adapted Out a lot of elements that made the light novels more enjoyable, such as removing many stories that featured side characters like Lisbeth and Silica, Argo being Demoted to Extra, and Kirito's personality being a lot blander with the aversion of his VR-geekery and existential philosophy. However, a lot of detractors state that the anime adaptation is overall very true to the source material and that even adding the Adapted Out elements wouldn't improve on the overall quality, so any blame for its many flaws should all fall to Reki Kawahara. In addition, the pacing problem and large Time Skips from the Aincrad arc are only present in the anime due to the light novels being collections of short stories that don't directly interconnect, but the anime took all of them and arranged them chronologically without trying to iron out inconsistencies or adding needed connective tissue, which makes the arc seem disjointed and rushed.
The Phantom Bullet arc as a whole. Did it successfully Win Back the Crowd with its new premise and a likable new female lead, or did it further contribute to the show's decline with its awful pacing, silly plot, and a new girl who is yet another addition to Kirito's harem? The only thing that both sides can agree upon is that it's hands down better than the Fairy Dance arc.
There's a bit of discussion about at which point exactly the series pulls off Win Back the Crowd after the Fairy Dance arc (for those who enjoyed the Aincrad arc) or Growing the Beard (for those who didn't like the show in the first place, but got on board later on). As mentioned in the previous point, there are people who consider Phantom Bullet to be this, but there are also those who champion Mother's Rosario, Ordinal Scale, or Alicization instead, each one for different reasons. And of course, there are those who think that the franchise never becomes good at any point, keeping their belligerence against those who think it does.
The Wish Fulfillment aspect of the series. For many detractors, it's the number one reason for the series being terrible and cringey, being so over the top that it becomes downright intellectually insulting, particularly in regards to the sexual fanservice of reducing female characters to sexual fantasies way too often. On the other hand, for fans Wish Fulfillment is exactly the main appeal of the series, and they see nothing wrong in enjoying the series because of it rather than despite of it. This is especially considering SAO is far from alone in this aspect and that there are other shows that are arguably even worse in this regard, even among popular ones.
Related to the previous point, there's Kirito and Asuna's romance. Detractors feel it completely ruins the story by taking away the focus from the Deadly Game premise and/or for being poorly executed by being too rushed (although the Progressive mini-series alleviates this part), having cringey dialogue in places, and/or being there just to pander to shallow romance fantasies. Fans on the other hand, consider the story to be is at its strongest when their romance is involved, even if you concede the Wish Fulfillment, since their Battle Couple dynamics offer a mix of action and romance that is extremely rare to find anywhere else. Plus, the fact that they get together early on and stay together ever since, no matter how much Ship Tease both parties may have with other characters, and without relying on Will They or Won't They? dynamics nor forced bickering between them, is considered even refreshing in a popular culture where romance stories and subplots almost always end with the couple getting together or are about the couple being in danger of breaking up (see Escapist Character below). Some go as far as to say that Kirito works much better as a character when he's with Asuna than when he isn'tnote These people used to say the same thing about Asuna, although the Mother's Rosario arc also toned that one down thanks to her relationship with Yuuki and the Sleeping Knights. Kirito's relationship with Eugeo in Alicization, though, did not have the same effect. Kirito improved as a character only in the eyes of the fans he already had, but he wasn't Rescued from the Scrappy Heap for his detractors like Asuna was with many of hers.
Asuna's lesser prominence in later arcs is another point of divisiveness. For those who consider Asuna generic and uninteresting, it's actually refreshing to see her step out of the picture to make way for other companions Kirito comes across. For those who do like Asuna as a character, having less of her is a reason to stop watching due to her being one of the main appeals for them. To a lesser extent, this also extends to all of the girls of the harem as a whole, with some wanting to see more of them and others feeling their presence ruins the series.
Related to the previous two points is the Supporting Harem itself. For a lot of detractors, precisely due to Kirito and Asuna being the Official Couple from very early on, the harem's mere existance is pretty much pointless, and impossible to justify outside of yet again just cheap pandering. For this people it's specially frustrating to see pretty much every single female lead of each new arc to be relegated to Kirito's harem once their time in the spotlight is finished, with little to none further development (Sinon and Alice are the most affected by this). Supporters on the other hand see not much problem with it, since all the girls are in the harem on their own volition, none of them have any delusions of ending up wining Kirito over, conscious or otherwise, and all support his relationship with Asuna. Not to mention that they end up forming quite solid relationships with each other outside of Kirito, forming a small Family of Choice of sorts. And even conceding the Wish Fulfillment aspect of it, they argue the fantasy of being the object of desire of a bunch of beautiful women, even if you have already given your heart to one of them, is quite alluring on its own and valid as long as you don't act maliciously about it, which they argue, Kirito never does.
As per the norm with the usual Subbing vs. Dubbing arguments, the majority of SAO fans consider Yoshitsugu Matsuoka the true voice of Kirito, to the point that they can't help but think about Kirito when they hear Matsuoka voicing other characters in other shows. Although Bryce Papenbrook is overall well liked among fans of the English dub, his involvement in other shows like Attack on Titan or the Fatefranchise makes him feel less associated with Kirito.
An odd case in the European Spanish dub with Darío Torrent for Kirito and Eva Bau for Asuna. Although Spaniard fans also vastly prefer the Japanese VO in this franchise, and despite the fact that both of them have dubbed other popular anime series before and after SAO, Torrent and Bau are often nicknamed "Kirito and Asuna's voice actors" by Spaniard anime fans when they appear in other showsnote Almost always as a derogatory. Not only because of SAO's infamy, but also because Torrent and Bau are considered cheap, lower-tier voice actors. So people aren't exactly thrilled when they are announced as main leads in any anime dubs, since it usually means the publisher is cutting corners in that department.
A similar case happens in the Latin American Spanish dub with the same characters and their voice actors, Luis Leonardo Suarez (Kirito) and Alejandra Delint (Asuna), except that, unlike Spain, both actors and their performance are wildly beloved, despite that both actors were basically unknowns before SAO.note In the case of Suarez, he previously worked in minor or secondary roles, like King in The Seven Deadly Sins or Valt Aoi. Alejandra Delint is a more extreme case, as she is a TV and commercial model, with some dubbing credits under her belt, mostly minor roles.
Cargo Ship: Kirito and sandwichnote one of the most popular joke ships in the fandom, stemming from how emotional Kirito becomes over the loss of his sandwich in Episode 6, and how Asuna seems to be able to control Kirito using sandwiches. It got to the point where people say that Kirito only married Asuna for the sandwich, or that he actually married the sandwich itself.
Similarly, Kirito and Eugeo rescuing Ronye and Tiese from the filthy clutches of Humbert and Raios and turning them into red-fountains with their swords will have you clapping and cheering. Gets better in Rising Steel, where you not only get to beat the crap out of them yourselves, but can fight them using Ronye, Tiese, and Frenica.
In Alicization Awakening, Suguha chopping off the arms of her assaulter Dee Eye Ell who had tied her up and attempted to life-drain her with leech tentacles, then one-shotting her with a single attack that turns her into a bloody paste on the field.
Also in the same volume, and episode 18 of War of Underworld in the anime, Asuna facing PoH alone and unleashing Mother's Rosario on him with the help of Yuuki's spirit/memory. Asuna hadn't had such a badass moment since the Aincrad arc, if not this being her most badass moment, period. All after years of a significant amount of people feeling that "The Flash" had lost her spark since the first half of season 1. To top it all off, the anime treats it with one of the most spectacular pieces of animation in the entire franchise.
And of course, from the same volume in the novels and same episode in the anime, Kirito waking up from his Angst Coma. Fans cheered with sheer joy after waiting for so long, and even some people who aren't that fond of the character were surprised to find themselves being so glad of seeing him back.
An interesting variant shows up in the Rising Steel mobile game. In the game, certain Hate Sink or Scrappy charactersnote Kibaou, Kuradeel, Jink, Raios, Humbert, etc appear as playable characters, often as 2 and 3 stars who are incapable of matching the 4 star units you'll likely be getting and using. In the game mode Ordinal Battle, you make up a team of up to four Units to beat the AI controlled team of another player, with your team being sent to fight other players while also controlled by AI. This means that, if feel like helping your fellow players score an easy win, you can put these units in your Ordinal Team, maybe even on their own, to be delivered a Curb-Stomp Battle by another player's vastly superior team.
Kayaba's debut in the pilot using the hooded "Game Master" avatar. It's immensely creepy where the sky turns red from being filled with "System Announcement" messages, before what appears to be blood drips out from the edges of the popups and pools together into the giant red-hooded avatar Kayaba is using.
Most members of Laughing Coffin give off this vibe, being a whole guild of Serial Killers, but PoH stands out the most, being garbed in a creepy hood and wielding a meat cleaver as his Weapon of Choice.
Death Gun. A Darth Vader Clone with a gun that can One-Hit Kill players and give them heart attacks in the real world. He's also an Implacable Man who never stops hunting his targets, and then it's revealed he's an SAO survivor like Kirito and a member of the Laughing Coffin. Sure, the reveal of who he is and how he pulled off the murders diminishes his creep factor, but his presence itself is still pretty unnerving.
Critical Dissonance: The franchise was one of the biggest commercial hits of the early 2010s, and still has quite a big fan base. You wouldn't believe it from anime critics, though, who for the most part hate it to a degree comparable to how most film critics hate Michael Bay movies.
Critic-Proof: Sword Art Online as a whole is easily the most controversial anime of the The New '10s, being the most simultaneously loved and hated on. The mere mention of the name is bound to start fights between fans defending it and haters bashing it. Countless YouTube critics have made names for themselves tearing the anime apart to the point where it ended up becoming "cool to hate SAO". Despite the overwhelming hatred it receives, it still performs well and continues creating new seasons, manga, video games, and films years after its debut. To say nothing of the light novel sales, which have hit over 26 million copies sold globally as of 2021 and are still going strong.
Crossover Ship: Fans believe Kirito would likely find a kindred spirit in Ren, due to the similarities in their character and their lives, both were alone on Christmas, both slayed a dragon and both know what it's like to lose their whole party.
Despite being The Scrappy, as stated below, there are fans who genuinely pity Kyouji, especially among Light Novel readers who are able to learn of his past of being bullied and his poor home life, which the anime largely Adapted Out.
Alice gets this treatment among strong Kiriasu shippers, due to her being the only girl out of the main cast making a move on Kirito despite him being in a relationship when the others have backed down for Kirito and Asuna's sake. See Unintentionally Unsympathetic below for more details.
There are times when Asuna is a literal victim of this, with some fanfic writers writing stories that either kill her off before or during the story so that Kirito can get together with their character of choice.
Despite having kidnapped and murdered thousands of gamers, Kayaba Akihiko's fans insist he is not evil because he isn't sadistic like Sugou Nobuyuki or Death Gun, despite the fact that Kayaba is directly responsible for the other antagonists being able to pursue their evil goals. Even more nonsensical is that he still has fans in-universe, such as Asuna and Kirito.
Quinella also gets this treatment to a much lesser extent. While the novels are ambiguous over whether or not her sociopathy is the result of merging her soul with Cardinal or if she always was one and can now express it completely, it doesn't change the fact that she's hugely selfish and seems to relish in the misery she causes others. Even the anime gets in on it by giving her a somewhat sympathetic sendoff where she dies content and with a smile on her face. Her status as a Shameless Fanservice Girlmay have something to do with it...
Dry Docking: The number of fans who are displeased at Kirito's guts and want him to stay away from any female character in the cast so they can have them for themselves is quite high.
Epileptic Trees: A very popular fan theory is that Kuroyukihime from Accel World (also by Reki Kawahara, set in the same Shared Universe two decades into the future) is Kirito and Asuna's daughter. Furthermore, her real name is theorized to be Sachi Kirigaya, due to her nickname being Sachan. This was officially debunked in Unital Ring with the introduction of Kuroyukihime's mother, who is not Asuna.
Escapist Character: Basically, the appeal of both Kirito and Asuna for their fans. Apart from the obvious escapist possibilities that they offer separatelynote which on the other hand are the ones that detractors find are taken way too far. See Base-Breaking Character above, they are somewhat unique in that they also offer an escapist fantasy for couples. As in living a great adventure with your significant other with both of youkicking ass together in pretty much equal measure. A type of fantasy that is actually quite uncommon, not only in anime, but in popular media in general. Especially to this degree and especially without being hindered by Will They or Won't They? dynamics, which SAO refreshingly never relies onnote A common point of praise is that Kirito and Asuna get together early on, rather that having an all-too-common Last-Minute Hookup, and most importantly, stay together through thick and thin. Despite all the Ship Tease that Kirito may have with his Supporting Harem, the story always makes clear that he has eyes only for Asuna.. This applies mostly to the Aincrad arc, obviously, and it's a big part of the reason why it's still the most popular arc... and why the Fairy Dance arc is so hated, for that matter, since it pretty much throws this fantasy out of the window in the worst way possible. Also the reason why the film Ordinal Scale, which focuses on their relationship, not only was very well received by fans, but also managed to recover some fans that had dropped the series (signaling that the creators are fully aware of this situation). Couples cosplaying together as Kirito and Asuna in tandem is a pretty common view in anime conventions because of all of this.
Quinella. There's those who like her for being a brilliant villain, and then there's those who like her for being one the sexiest females period. She spends the majority of her appearances completely naked with nothing but Godiva Hair to cover up. This applies even more so in universe, where she's seen as the World's Most Beautiful Woman. Even Eugeo and Kirito acknowledge that her appearance is "perfect," to the point of making Alice and Asuna look plain in comparison, despite seeing her as the Complete Monster she is.
PoH is considered this In-Universe, and certain parts of the fandom can't help but agree, especially when his younger self was shown in the flashback sequences.
Calling the Fairy Dance arc (Season 1 Episode 15-25) "Season 2". Fans get very irritated when people get it mixed up with the actual Season 2 titled "Sword Art Online II".
Saying Kayaba was never given a reason behind trapping thousands of players in SAO, due to his line saying that he forgot the true reason. Fans will adamantly point out it was literally explained right after that he wanted to create a real virtual world and that he had fulfilled that dream.
Calling Underworld a "game" despite the story making it very clear it is a top-secret virtual simulated environment populated by AI, being used for a government experiment funded with a black budget. Yet the misconception continues to persist.
Due to Alicization being split into two halves, there's the tendency of people referring to War of the Underworld as Season 4. Though this one does have some justification as the production does tend to bill them as separate seasons and get listed individually rather than together. One could even get away with saying that the anime turned them into separate seasons even if they weren't in the light novels.
It is very common for anime-only watchers to make comments like "I haven't read the manga" or "where does the anime leave off in the manga?" Due to this franchise's status as a Gateway Series, a lot of newcomers to the anime scene are not familiar with Light Novels and how they have become so prominent as source material for so many anime starting in the 2010s, and think the show is based off a manga like other popular 2010s anime gateway series such as Attack on Titan and My Hero Academia.
There has been one with Log Horizon, due to the similar premise. Interestingly enough, many Log Horizon supporters seem to be former SAO fans that dropped the series at some point (normally when the focus of the Aincrad arc shifted to romance, or when the Fairy Dance arc started).
Hilariously, Hollow Realization has you in a massive single floor area, instead of a tower, with the player characters the only ones who can't die, while Non Player Characters who go into battle die for real... EXACTLY like Log Horizon
To a lesser extent, there's also one with Accel World, which is written by the same author.
...which has got several crossover elements with Sword Art Online in the video games.
Berserk fans have also not taken well to the fact that "The Black Swordsman" is now more commonly associated with a 16 year old gamer instead of an adult who actually wields a sword. It doesn't help that Kirito's sword in Alfheim is nigh-identical to the Dragonslayer or that both series author's use rape a lot (partially justified in Berserk's case for being a Crapsack World filled with adult battle-hardened characters as well as inhuman antagonists whereas SAO is NOT.)
Hollow Realization introduces a character, Genesis, with that moniker as a nickname, who bears a much closer resemblance to the original Black Swordsman. Ironically, HE is seen as the pretender in-universe, in exactly the same way that the Berserk fanbase saw Kirito as the pretender to that name.
Many .hack fans are also resentful of the fact that SAO is considered to have an original set up. Both works were created the same year, but SAO didn't become mainstream until it was formally published 7 years later.
With KonoSuba and Overlord, due to the similar premises as well as being the most commonly cited series that haters champion as being superior. With KonoSuba it helps that it did not Follow the Leader after SAO like most isekais did and completely deconstructed the cliches, along with the fact that KonoSuba has a memetically good reputation while SAO has a memetically bad reputation. While with Overlord the claims are that it took the same core concepts and ideas, such as an overpowered main character trapped in a video game but executed them correctly.
With JoJo's Bizarre Adventure, with said fandom constantly picking fights with the SAO fanbase, whenever SAO performs better in popularity polls. It's a reoccurring trend for JoJo fans to raid areas occupied by SAO fans and champion their show as the superior series.
A portion of fans of the anime see Aincrad as the only arc due to the many problems Alfheim had. There's also another portion which would do so too were it not for the arcs after it. Even the series itself doesn't really ever bring up Asuna as Titania afterwards despite Aincrad being referenced plenty of times.
The last episode of Season 2 and the ending of Volume 7 is this for those who were fans of Yuuki and didn't like the fact she died, to the point that many prefer the video games for sparing her from this fate.
Eugeo/Alice. Rather than the Ship Tease between Eugeo and various other girls or Alice as another member of Kirito's harem, nearly all fans support this couple. Even merchandising and Reki seems to get in on this, with a lot of official or promotional art depicting them together, sometimes with Kirito and Asuna in what looks like a double date, and the If You Were Here and If You Wish It side-stories giving them some Ship Tease with Kirito appearing to be a Shipper on Deck.
Arguably more popular than that is the Foe Yay pairing of Eugeo/Quinella, which got a huge boost after the anime. It helps that in the anime, she is not already nude when he enters her chambers, and takes the time to unlace her dress right in front of him.
Alice/Eydis. Thanks to Rising Steel featuring heavy Les Yay moments between them, these two have now become heavily shipped.
Fashion-Victim Villain: Sugou's Oberon avatar gets hit hard with this, with all of its fairytale king imagery making him terribly hard to take seriously. Even worse, while Asuna wearing barefoot sandals in her Titania avatar makes sense from an aesthetic point of view, as fairies are often portrayed in art as unshod or even entirely unclothed (not to mention she is technically a captive), Oberon wearing sandals is another thing, given that he has to fight and look dominant due to his role in the arc, and instead he just looks like a goofy tourist.
Klein struggling against the boar is played for laughs, but at the time, he and Kirito didn't know that dying in the game kills them in real life. If Kirito wasn't there to teach Klein, the latter would have died at the start of the game. Worse yet, Klein isn't the only one new to the game and not everyone had the good fortune of meeting a beta tester.
It's really hard to laugh when Kirito accidentally grabs Asuna's right breast after seeing Asuna nearly getting raped much later.
Shinichi's occasional creepiness trying to win Suguha's heart is funny because he's harmless. On the other hand, Kyouji turns creepy right before he tries to rape and murder Sinon. Before this, the two were very similar.
Gateway Series: For many western viewers, Sword Art Online is not only the gateway series for the isekai genre but for anime in general, being The New '10s equivalent of Dragon Ball Z. As much as many people hate to admit it, SAO was what got them into anime to begin with.
Genius Bonus: System Call and Code 871note Seal of the Right Eye are actual computer terms which programmers may recognize. A System Call is when a program tries to interact with the operating system, while Code 871 is when a program tries to modify something it does not have access to.
Germans Love David Hasselhoff: The franchise is surprisingly popular in Mexico. This is especially worth mentioning here for a myriad of reasons since no one, not even their fans, expected SAO to be popular there, partly because, unlike other very popular anime franchises popular in both Mexico and other Latin American countries, like Saint Seiya, Sailor Moon, Dragon Ball and even cult stuff (in Latin America) like My Hero Academia, Naruto or Bleach, SAO is not based on a manga (despite having one later on), but on a light novel, a genre which is even more niche in Mexico than Manga or Anime, due to its ties with regular literature, considering Mexicans aren't known for reading books at all.note Mexicans have one of the lowest levels of reading in Latin America, as reading books is normally reserved for academic or professional reasons, most of the time mandated by the requirements of those jobs. Reading for pleasure is considered a nerdy hobby, and sometimes, in the worst cases, it could be grounds for bullying or teasing. Most Mexicans prefer to read newspapers, magazines, comic books, the Internet, or other kinds of visual media that have something besides lots of text.
Gotta Ship 'Em All: One solution fans have to the Harem Genre in the series, is to pair the many members of the harem up with each other, with Lisbeth/Silica and Leafa/Sinon being popular pairings.
In regards to the anime, while the series starts off pretty strong, it's the two-parter in episodes 5 and 6 where they really get the comedic timing down and solidified Asuna's characterization. The light novels are a different story due to the anachronistic nature of the first two volumes. Episode 8 is also considered as such, due to dropping the independent episodic story format in favor of a continuous flowing narrative.
After the extremely controversial Fairy Dance Arc, the Phantom Bullet Arc is widely considered to have redeemed the show with its increased focus on storyline and Character Development, while keeping the continuous flowing narrative as opposed to the episodic stories in the first half of the Aincrad arc. Mother's Rosario also follows suit by giving Asuna some much needed depth after many had considered to be undeveloped.
The Alicization arc is extremely highly regarded among fans and praised as Kawahara's best work for SAO. It features a very compelling story line that avoids the rushed pacing issues of its predecessors, giving focus to many characters other than Kirito (with Asuna eventurally taking up the role of Deuteragonist once again), and delving very deeply into existential philosophical of human nature. It also introduces Alice and Eugeo, possibly the two most popular SAO protagonists (aside from Sinon and Yuuki).
One of Sugou's many vile acts was being a sexual sadist. An already dark moment gets depressing after his voice actor in the English dub, Todd Haberkorn, got hit with a rape allegation in January of 2019 by Jessie Pridemore note She kept him anonymous when talking about her rape in relation to an incident with Vic Mignogna, but Todd chimed in not long after saying that he was the one Pridemore saw and claimed it was consensual..
The subplot about Koreans being left off from The Seed Nexus (which is the basis of the VRMMO after Aincrad) and how it incensed at least several players including one particular POV character during one chapter of Alicization Awakening becomes quite relevant after increasing tensions between Korea and Japan due to trade restrictions for high-tech materials in July 2019.
He Really Can Act: For anyone with complaints about Yoshitsugu Matsuoka using nearly the same voice for all his characters, he really makes up for it in Alicization. Not only is he voicing Kirito as a kid, but he's also evolved the now older Kirito's voice making it noticeably deeper than the Kirito introduced in Season 1. And for the really sceptical about his range, at the end of the arc you have his Star King Kirito voice, which he uses briefly for the real Kirito as he returns to the real world after his 200 year reign in the Underworld, but most impressively, for his copy. Matsuoka manages to really sell a much more experienced and worn out Kirito, with a slightly off touch that borderlines on Uncanny Valley to give the impression that those 200 years really made a number on his state of mind, but without being able to put your finger on it.
Kirito's statement at the end of the Aincrad arc that "there's nothing more boring than watching someone else playing an MMO." Back in 2002, when the webnovel was written, most people would have agreed with him. Fast forward a bit over a decade later, when the success of Let's Play videos and gaming streaming platforms has made that statement age quite poorly.
The fact that there is an arc called, "Mother's Rosario." Kirito's birthday is the Feast of the Rosary.
The titular Sword Arts, as described in the novel, are special attacks where the system briefly takes over limb control, activated by specific arm movements. In other words, motion controls five years before the Nintendo Wii popularized them.
Episode 10 of Alicization and the above-mentioned Goblin Slayer aired on the same day, and in a truly ironic coincidence, Alicization was the serious, intense episode that featured (attempted) rape and buckets of blood, while Goblin Slayer was a calm and slow-paced episode devoted to character development and relaxation. Jokes abounded about how the two shows must have gotten their scripts mixed up.
During The Girl of Morning Dew Kirito tells Asuna a ghost story. Coincidentally, they find a ghost in the forest, who turned out to be a girl named Yui. It was later revealed that Yui was an Artificial Intelligence. Hmm... A ghost that turned out to be an AI. Sounds familiar, doesn't it?
Oodles between Kirito and Klein. Many fans even include Klein as part of Kirito's Supporting Harem.
Starting in the very first episode. In the Japanese version of the first episode...
Klein: Kirito! ...Ah... Hey, Kirito. You were actually pretty cute. That's my type. Kirito: And that unkempt face of yours suits you ten times better.
Kirito and Eugeo. Kirito describes Eugeo, his "partner" throughout his adventures in the Underworld, as one of the few very close male friends he's had, and hopes to introduce Eugeo to his friends. Eugeo's death hits Kirito very hard, leaving him broken in spirit for quite some time. In fact, he takes Eugeo's death in some ways worse than he took Sachi's back in Aincrad.
A strange example happens early on in Phantom Bullet, when Sinon is significantly friendlier to Kirito when she thinks he's a fellow female player.
Asuna and Sinon. In the light novels, it's said that shortly after meeting Asuna, Sinon decided to try to overcome her trust issues and give friendship a chance. The two are on a First-Name Basis by the end of their first meeting; compare that Shino being on a Last-Name Basis with Kyouji, whom she's known for some time. By the start of Alicization, not only has Asuna started using the Affectionate Nickname of "Sinonon" on Sinon, but she also invited Shino over to her house.
Asuna and Yuuki during the Mother's Rosario arc. When Asuna suggested Yuuki marry someone, Yuuki jokingly considered marrying Asuna. In her dying moments, Yuuki also said Asuna was the person she loved.
(Asuna's perspective): She gasped in shock. An astonishingly beautiful knight with snow-white skin, roughly the same age as her, was glaring at Asuna. Her sapphire eyes emanated an animosity that seemed to crackle like electricity. Her golden hair, seemingly fashioned from the element itself, billowed in the air. Her hefty armor and smooth longsword both gleamed a flaxen yellow. (Alice's perspective, a little later): Or was it because Asuna was so extraordinarily beautiful that just looking at her made you sigh? An exotic face without even the slightest tinge of austerity, as though it were the embodiment of the word exquisite itself. The bonfire brightly illuminated her white skin and her soft, billowing chestnut hair, which looked to be top-quality strands of silk braided together. The Guard Leaders' eyes all revealed intoxicated gazes of admiration. If Asuna had called herself Goddess Stacia, they would have believed her without question.
There's even more in the gameverse, see this page for more details.
SAO is one of the biggest examples in the entirety of fiction. It garnered excessive attention and for a while became the most hyped anime of its time. However many came out of the experience with negative opinions, especially the Fairy Dance arc. In fact one of the main reasons people started rigorously hating on it was because of its popularity and the belief that it was undeserved. And then the critics got their hands on it and thoroughly destroyed its reputation, where SAO went from the darling of the anime community, to its favorite punching bag.
The Alicization arc, which was heavily hyped as the best SAO story before its anime adaptation began, also got hit by this to an extent. The opinions from fans were overall positive, but a significant amount of them don't consider it the best arc, due to a relatively slow beginning, the sidelining of the supporting cast (although they think Eugeo and Alice makes up for it) and the story moving away from the video game setting being a somewhat divisive move. And of course, at the end of the day, it didn't manage to sway the opinions of detractors, some of them being former fans, who think that Alicization does nothing to fix the flaws of the franchise, as they found instances of illogical plots and plotlines, underdeveloped characters (and this time not even Alice and Eugeo escape this criticism, the latter not being helped by detractors pointing out his design is just a Kirito palette swap), yet another use of Attempted Rape as a plot point, and the use of sexual fanservice, particularly with Quinella.
It's Popular, Now It Sucks!: Sword Art Online was one of the first Gateway Series of The New '10s, being one the most hyped series at the time of its release. However its surge in popularity and introduction to a wider audience was what contributed to it becoming a critic-favorite punching bag. The wider audience allowed its flaws to become more pronounced, which then escalated as more and more people jumped on the hate bandwagon leading it to became trendy to hate SAO. In fact its the popularity of the series itself which is in part what leads to the extremely vocal hate, with the detractors stating the series does not deserve such popularity.
Jerks Are Worse Than Villains: Many of the Hate Sink characters end up falling under this and end up more reviled than the proper villains (except Sugou, who earned his Hatedom and is much worse than the jerks mentioned below).
Kibaou in the anime, garnered a lot of disdain due to his extremely callous and prejudice behavior towards Kirito and beta players.
Endou from the Phantom Bullet arc, an Alpha Bitch who delights in bullying Sinon over her PTSD. She is far far more reviled than the arc's actual villain, Death Gun, despite her crimes being much tamer in comparison.
Raios and Humbert from Alicization, two arrogant noble disciples and Kirito and Eugeo's personal bullies at the Swordcraft Academy. While they do end up slipping firmly into evil territory, they are still far more tamer than the Big Bad Quinella, yet it is these two who are far more despised by the fandom for their Attempted Rape on Ronye and Tiese.
The series itself for a quite big portion of their detractors, including some high-profile critics. These people find bashing the series to be genuinely fun in it on itself. Ditto Kirito himself. This is a big reason why the hate bandwagon is so long lasting, even during long periods of time without any new SAO anime material.
Quinella is one of the most loved BigBads in the series, due in no small part due to her attractiveappearance and lack of clothing thanks to her ascension. There's also the fact that she's easily the most complex villain to date with her entire backstory provided and her ascension to power described in detail.
While PoH didn't get this treatment in the first arc due to his lack of screen-time, his re-appearance in War of Underworld gave him a great raise in popularity due to the legitimate threat he poses, especially when he logs back in with an army of foreign players, his rather hammy mannerismsnote "GoodMorning!", his actually rather tragic backstory, and just how cool and intimidating his abilities and weapon are. Ironically enough, this how he feels about Kirito In-Universe, stating that he loves him for how much of a pain of the ass he is to him and how impossible he is to corrupt.
Akihiko Kayaba is a brilliant programmer desiring a fully-immersive Virtual Reality simulation and creator of Sword Art Online, the world's first VRMMORPG: trapping 10,000 players within and setting it so they die in real life if they do in the game while preventing authorities from stopping his game. Disguised as Heathcliff, a charming leader of a group of players within Aincrad, Kayaba reveals himself when hero Kazuto "Kirito" Kirigaya deduces his identity and duels the latter, releasing the players and seemingly killing himself when beaten but in reality sending his Fluctlight to continue existing on the internet. Reappearing out of disgust for the next season's Arc Villain, Kayaba assists Kirito in defeating the antagonist and entrusts Kirito with his final invention: made to allow others to create their own virtual reality games and have it shared with the world. Returning once more in the Alicization arc, Kayaba helps save the virtual reality world the heroes are within by taking control of a robot in the setting, proving himself Kirito's most honorable foe.
Seijirou Kikouka masquerades as Kirito's benefactor but in reality is a JSDF lieutenant colonel leading RATH, the creators of the virtual reality world Underworld. Swindling Kirito into working for him, he hopes to use the artificial Fluctlights of Underworld as soldiers to avoid human casualties in war and when Kirito is hospitalized, Kikouka has him connected to the virtual reality world, hoping to save his mind out of genuine concern. When attacked, he helps fight the sociopathic Gabriel Miller and through the series learns to value the AIs he once sought to use as Cannon Fodder to save human soldiers, successfully escaping after showing Japan's potential at the arc's end.
Memetic Badass: Kirito in a rare derogatory example of this trope. His Plot Armor is said to be unparalleled and he can never die no matter how unlikely survival is.
Kirito himself tends to get this from the periphery hatedom, who will endlessly bring up the fact he's a loner gamer with no social life and is only so strong because he endlessly grinds like a loser, rather than the badass swordsman the show makes him outnote even though in the real world he's able to fight off Sugou and spar evenly with his kendo champion sister Suguha. Furthermore, pretty much every versus topic that features Kirito will have the majority of people rooting for the opposition and coming up with every possible way to make Kirito seem weak and lose, regardless of whether or not it makes sense in the fight.
Argo. Kirito and Asuna are pretty much her play things. She will go to great lengths to embarrass Kirito and it's absolutely hilarious. The fact she's an Knowledge Broker who's Only in It for the Money has led her to exploit the most sensitive and personal of information and sell it off for cash, or the lows she will stoop to getting said information in the first place. Then there's the fact she keeps insinuating Kirito has a thing for her, mockingly treating every one of his attempts at being friendly to be flirting.
Lisbeth is known to notoriously troll Kirito and Asuna. She loves putting the lovey-dovey couple in awkward situations, while she's most likely the one to kill the mood by telling them to Get a Room!. She's also not afraid to get physical with other girls, or snuggling up to Kirito despite the fact he's in a relationship.
Sinon serves as the Arc Hero of the Phantom Bullet arc, where she takes over from Asuna as the female lead much like Leafa did. However unlike Leafa who ended up being a Replacement Scrappy, Sinon ended up being a welcome change and would go on to become a Breakout Character. Fans praised her for her compellingpersonality, her much deeper backstory, having a more realistic motivation for taking up gaming, as well as being the first female protagonist who is not defined by having an interest in Kirito. There's a large group who wish Sinon was the solo protagonist of the GGO arc without having to share the limelight with Kirito.
Alice, who might just be the most positively received female lead yet. While she's loved for being a similarly strong heroine much like her predecessors, she avoids the flack that many of the past SAO girls get by not being dependent upon Kirito and prove to be formidable and badass completely on her own.
Quinella to Sugou. While all of the villains that came after him were more popular due to Sugou being reviled by the fandom, special mention goes to Quinella who might very well be the most popular SAO villain to date. She's deemed a far more complex villain and a far bigger threat, while Sugou was extremely one-dimensional and pathetic. She also has a very large following due to her invoking Evil Is Sexy.
Sigurd from the Alfheim arc. He quickly establishes himself as a Jerkass when he tries to boss Leafa around outside of the scope of their original agreement, and when Kirito calls him out on it, Sigurd threatens to kill him when he can't fight back. As such, it's not especially surprising that he's the traitor in the Sylph faction, even if the twist is more about there being one than who it is.
From the Progressive Series, we have Joe, who's all but confirmed to be a member of the PKer Conspiracy led by PoH that dedicate themselves to hindering the frontlines. Even before the implications were brought forth, Joe never helped his case with his constant rantings that the ALS should take a mistrustful stance against Beta Testers and the DKB, even at times where it serves to benefit no one and could potentially get someone killed, and tried to get Nezha and the Legend Braves executed by the Clearing Force with unreliable info that their scam killed another player. The Manga is especially gratuitous with this by depicting him as wearing a hood similar to Morte's right before the arc where Morte himself is revealed as a member of the The Conspiracy.
Older Than They Think: While the light novels began publication in 2009 (with the anime not starting until 2012), Reki Kawahara actually started writing SAO related stories as early as 2001 with the intention of competing for the 2002 ASCII Media Works' Dengeki Game Novel Prize. After being rejected for surpassing the contest page limit, he published it on the internet immediately after and kept adding new stories in that format until 2008 (with Alicization specifically written from January 2005 to July 2008), going as far as completing the Alicization arc and writing the beginning of the Moon Cradle arc. The light novels are edited versions of those original stories, with certain moments (i.e. Kirito and Asuna's first time) Adapted Out while also toning down some other elements (such as Asuna originally being the one to kill Kuradeel in Aincrad, or Eugeo being too late to save Ronye and Tiese from being raped for real in Alicization). Many fans, especially those who got interested in the series because of Alicization, are surprised to find out the source material for the anime was already over a decade older than its debut in October 2018.
Episode 1 of Alicization has a lot of these in the form of characters from other SAO media having cameos.
Kureha and Zeliska from Fatal Bullet can be seen at the bar playing pool. While both Kureha and Itsuki's names can be seen on the 5th BoB rankings.
Overshadowed by Controversy: The rape scenes in Sword Art Online are considered to be the most controversial aspect of the light novels. Episode 10 in the Alicization arc had a rape scene was so graphic and disturbing that the episode was censored by Aniplex USA and the light novel's author even personally apologized to the voice actresses of the two characters who were raped in that scene and gave a full explanation as to why he wrote the rape scenes in his work.
And there is always the possibility that when Deep-Immersion Gaming is invented in a decade or two that it won't be as safe as it was intended to be. There are a bunch of ways to die with a Nerve Gear that DON'T involve product tampering. The fact that you're completely paralyzed means that if there was some emergency, such as a fire, you would be completely helpless because you'd have no way of knowing that you were in danger.
The concept of Death Gun, a Serial Killer who can somehow kill people in a video game despite that being seemingly impossible without NerveGears, is already plenty disturbing but The Reveal of exactly how Death Gun kills people is equally disturbing. After stalking players in GGO and finding out their personal information, including where they live, Death Gun's accomplice breaks into the real life house and waits for the Death Gun in the game to shot the target before injecting the victim with a lethal drug overdose. Sinon herself almost has a complete Freak Out when she realises that there is a deranged Serial Killer quietly watching her unresponsive real life body waiting for the moment he can kill her.
The disappearance of PoH's body from the Ocean Turtle with no explanation. Despite the fact that Kirito turned him into a tree in the Underworld to ensure he can never leave, his body mysteriously disappears from the STL room between Critter discovering him and Gabriel's corpse and the other GDS soldiers going there to recover Gabriel, with none of them ever finding his body.
Episode 38 of Alicization ends with the souls of Bercouli and Quinella flying off into the sunset on his dragon right after they exchanged a rather heartfelt conversation about their long lives before she softly takes his hand and sits in his lap to ride off with him. The last bit was a change from how the light novel portrayed it, as in the novel, Bercouli flew off on his own without Quinella. The anime's version of the scene apparently got enough people to start mistaking it as a shipping moment that Reki Kawahara himself had to debunk it on his Twitter by denying there was any romantic feeling to it and comparing it to more of an awkward boss and subordinate relationship.
Debate has raged since the Phantom Bullet arc on whether or not Sinon has romantic feelings for Kirito, not helped by how frustratingly ambiguous she acts in a lot of scenes when she's around him. Episode 39 of Alicization brought this to a head when Sinon reveals to Alice exactly what Kirito is to her. Viewers noted that Sinon uses language that could be interpreted in a pretty romantically-charged manner when she says "I like (好き suki) Kirito... I like (大好き daisuki) him so very much. That's the same for Asuna and the others. And we're all worried about Kirito." Again, more insight had to be gained from Kawahara's Twitter commentary on the episode which explained that 好き suki in this case isn't supposed to mean feelings of "like" or "love" (and he specifically used English for those two words in his tweet) and that even an interpretation of it as "partner" or "comrade" still isn't quite accurate. In his mind, it's more of a case of a bond between souls that have overcome heavy burdens together.
Leafa was initially hit by this, due to taking over Asuna's role as the female lead during the Fairy Dance arc, where there were Squick elements due to the fact she is in love with Kirito while being his real life biological cousin and adopted sister. It doesn't last in later arcs, however, once the romance aspect is dropped and she goes back to being Kirito's supportive Little Sister Heroine.
Gabriel is this to Quinella. While Quinella is beloved as a Love to Hate villain and had a huge fan following, Gabriel became a very polarizing Base-Breaking Character with some considering him to be a worthy replacement to Quinella, while others thoroughly despise him and wish Quinella stayed around.
The Mother's Rosario arc saved Asuna in the eyes of many of her detractors. She ends up getting a fair amount of Character Development in gaining the same confidence she had in SAO in real life, and at one point, even passes up an opportunity to call up Kirito so that she can deal with her own problems.
Leafa/Suguha fights off her detractors after the Fairy Dance arc where her Kissing Cousins aspect gets dropped and she goes from love interest to Little Sister Heroine. She has it even better in the gameverse where it overlaps with Better Than Canon, as the romance plot is avoided altogether as she knows straight from the beginning that Kirito is her brother.
Kirito gets this treatment for quite a few in the Phantom Bullet arc, due to his effeminate avatar in GGO. This version of Kirito dubbed Kiriko, is incredibly popular both for design and adding an interesting twist to Kiritos personality and character. It's not uncommon for people to declare that Kirito is best girl. And then Kirito further gets this in the Alicization arc with many of his past detractors deeming him much greatly improved as a character due to his Bromance with Eugeo, which fleshed Kirito out as a character.
Kirito is heavily subjected to this by critics and reviewers who try hard to make him look like an awful person that is selfish, narcissist, manipulative, and hurts people close to him like the girls that are part of his harem. For instance one meme has Lisbeth telling Kirito she loves him and he replies on how he loves himself too.
Asuna's mother, Kyouko Yuuki, also gets this treatment. Despite being, at worst, a concerned but ignorant and overbearing motherwho has a point on Asuna's limited education prospects and resents VR and her daughter's fascination in it for good reason, most fanfictions tend to depict her as being more antagonistic and controlling of Asuna, as well as more abusive. And while a lot of them keep her HeelFace Turn, some outright make her the Big Bad who resorts to shady means of getting what she wants. She's also sometimes depicted as a Manipulative Bitch who uses Exact Words in regards to the deal she made with Asuna at the end of Mother's Rosario, saying she only agreed to let Asuna keep attending the Survivor's School and that she's still forcing her to meet suitors, despite Ordinal Scale showing that she's at least willing to give Kirito a chance.
An likely unintended and non-malicious variant often occurs with Sinon. In canon, Shino was willing to forgive Kyouji for his role in Death Gun and trying to kill her, and was determined to try and save him as person by visiting him and giving her support to his rehabilitation, with the first volume of Alicization revealing that she's succeeding in this regard. Most fanworks however tend to depict her as outright fearing or hating Kyouji and not willing to give him a chance, likely due to the writer's own feelings on the character or feeling that there's no chance they could ever be friends. This is especially prevalent stories that pair Shino with Kirito or an OC where he appears as an antagonist for Kirito/the OC to save her from, wherein she often treats him like garbage and makes no attempts to reason with him despite her canon actions in regards to him implying that she would be more sympathetic and plead for him to make a HeelFace Turn, and many fics adapting Phantom Bullet tend to leave out her asking to visit him to help in his rehabilitation.
Due to how the Illfang boss was adapted from the Progressive Vol 1 to the anime, Kiboau is heavily subjected to this. In the Light Novel/Manga canon, Kiboau was something of a Jerk with a Heart of Gold who was often comparatively more reasonable than his rival Lind, who was the the actual person who drove Kirito to becoming Beater by accusing him of causing Diavel's death. The anime making him a Composite Character for Lind, making him the one to accuse Kirito of letting Diavel die instead of the Adapted Out Lind, turned him into an outright Jerkass who lacked the Hidden Depths he originally possessed. As a result, whenever he's written into any stories taking place in Aincrad he's presented as outright antagonistic, even ones that closely follow Progressive. It doesn't help that many official materials, such as the Rising Steel mobile game, tend to follow the anime's canon and keep in him in his Composite Character role.
The other girls are sometimes depicted negatively by fans depending on who they pair Kirito with, with the girl they choose being presented as the best option for him while the others(especially Asuna if it's not her) are often Clingy Jealous Girls or outright Yanderes, despite the fact that a lot of them, with the exception of Alice, are shown in canon as trying to move on from him and let him and Asuna be happy together. Not helping matters is that the game's canon tends to depict them as exactly that, actively having them ignore the fact that Kirito's already in a happy relationship to pursue him personally while treating Asuna's understandable aggravation with this as part of the humor.
The game's Character Exaggeration of Klein's Casanova Wannabe tendencies can be seen as this, and often leads to similar depictions in fan works, making him appear a lot creepier than he does in canon, where he at least has some semblance on maturity and gentlemanly behavior. An example of this is an event in Hollow Fragment where he, upon hearing that Leafa has trouble waking up in the morning, makes her an alarm clock with a recording crystal, with the "alarm" being him whispering compliments into her ear, something most people would see as Stalker with a Crush behavior.
The Fairy Dance Arc is widely deemed to be the low point of the series by fans and haters alike, with reasons ranging from the treatment of Asuna, the series changing the Death Game premise to "save Asuna", the series becoming more like a harem, Yui's role change from mysterious adopted daughter to being a moeMs. Exposition, the Kissing Cousins element brought by Leafa crushing on Kirito, and Sugou as the most ridiculous and hateable villain, among others. Some fans even refuse to acknowledge the entire arc and go straight from Kirito waking up from SAO to meeting Asuna (freed from ALO) in real life for the first time.
To a lesser extent all of the post-Aincrad arcs get subjected to this to some degree because Sword Art Onlinestopped being about the titular game and instead kept bringing in new games. It's a very common view among fans that Aincrad should have been the only arc in the series, and instead expanding that out to the whole 100 floors. This ended up getting done in the video game continuity, although it still continues past Aincrad.
Ship Mates: As noted in Ship-to-Ship Combat below, those who ship Asuna/Yuuki and Kirito/Sinon tend to support the other for effectively getting the other in the canon pairing of Asuna/Kirito out of the way without issue.
Asuna/Yuuki is extremely popular, with Yuuki being a fan-favorite and Asuna being deemed at her best when she's with Yuuki, with lots of people preferring this over Kirito/Asuna. It's not hard to see the ship fuel from the sisterly bond the two share and the scattering of Les Yay moments between them including Yuuki jokingly considering marrying Asuna.
Kirito/Sinon. Sinon is frequently considered to be more interesting than Asuna and with shippers wishing she ended up with Kirito instead, there's also the fact she and Kirito are more alike than Asuna, with both of them being stoic and burdened by Survivor's Guilt.
Kirito/Eugeo. The Bromance these two share at times appears to reach far more than merely being Best Friends and more akin to significant others. In an official poll, Eugeo ended up scoring as the second most popular member of the "Kirito Harem" right behind Asuna.
Eugeo now finds himself caught between three major shipping factions. Those are Kirito/Eugeo, Eugeo/Quinella and Eugeo/Alice. Even after his death there are plenty of fics involving him getting with one of the three, with varying degrees of spite towards rival ships.
Kirito/Sachi. Despite it being obvious Sachi was never meant to be the female lead, a lot of people wanted this relationship to happen. Unlike Kirito's relationship with Asuna, which many felt was rushed and came abruptly, Kirito and Sachi were given proper reasons for developing feelings for each other.
Due to the Ship Tease they get in the War of Underworld, and with him later proposing to her in Moon Cradle, the pairing of Tiese/Renly has been involved in these. While it has a good deal of supporters, believing the two make a good match and feeling that Tiese deserves to move on and be happy, there are certain fans who are vehement in their support of Eugeo/Tiese, in spite of Eugeo's death and the implications that, while he cared for her, he didn't feel the same way she did.
Kirito turns into a Gleam-Eyes using an Illusion Spell.
How Kirito deals with General Eugene. Creating a giant smokescreen allowing him to grab Leafa's sword, asking himself with sun as he dives at Eugene, then using this second blade to block Eugene's Infinity +1 Sword where Kirito then goes Dual Wielding on him without system assist.
Phantom Bullet arc:
Sinon diving off a building, getting her leg shot off and still landing a Boom Head Shot on Behemoth.
Kirito's final battle with Death Gun, where his SAO avatar gets superimposed over his GGO avatar, with his two iconic swords taking the place of his photon sword and pistol.
Mother's Rosario arc:
Asuna and Yuuki's duel.
All of the SAO gang playing Gun Gale Online, with different looking avatars to the ones they had in Fatal Bullet, Asuna even has a Photon Sword!
Kirito Dual Wieldinghis and Eugeo's Swords against Quinella, while using Incarnation to manifest his Black Swordsman outfit.
Slow-Paced Beginning: To some, the beginning of Alicization in the light novels. The series begins with a young Kirito in a virtual world with Eugeo and Alice, with no explanation of what he's doing there. After a scene at the Dicey Café that includes some exposition, there's the Wham Episode-worthy twist of Kirito being attacked by Johnny Black, resulting in him suffering brain damage and having to be put into Underworld again, but it takes a few episodes/until the next volume for readers to learn what exactly happened.
The Fairy Dance light novel reveals that during Leafa's confrontation with the Salamanders before Kirito saves her, there are certain types of players called "Woman Hunters" who take advantage of how the Anti-Harassment Code doesn't apply in PvP in order to grope female players and, in some cases, derive some kind of sexual thrill from killing them.
The infamous tentacles scene Asuna is subjected too, which was the point where a lot of people gave up on SAO. It invokes All Anime Is Naughty Tentacles that's a better fit for a hentai genre.
The attempted rape on Asuna. The act itself was already bad enough to Squick a lot of fans, even to the point of making them drop the show. But it's even worse in how it's portrayed: The way Kirito saves her is seen by many as an empowerment fantasy. Even people who don't mind the Wish Fulfillment aspects of the show think that Kawahara went way too far in that scene.
Unsurprisingly, Sugou (the perpetrator of the act) was squicking the audience since his very first appearance. Just the way that he sniffed Asuna's hair in the hospital with that sick smirk on his face is enough proof that his Complete Monster label was never meant to be a surprise reveal.
Strangled by the Red String: In the Alicization anime, Iskahn and Sheyta go from sharing a Foe Romance Subtext to being soulmates in the space of the battle's time, which doesn't amount to more than a couple days maximum - and most of it offscreen. Not helping matters is how the anime cut out some Ship Teasey inner dialogue, such as after their duel where Iskahn contemplated capturing Alice so he could request Vecta to spare Scheta.
Suspiciously Similar Song: "Swordland" is by far the most iconic theme from the series, but many detractors immediately point out the similarities to another theme previously composed by Yuki Kajiura: "Rule The Battlefield", from Fate/Zero. To be precise, the first few notes of the main riff are pretty much the same. This can be better heard with "In You Past", one of the variations of "Swordland", which has a closer tempo and tone to "Rule the Battlefield", and thus the similarities become much more obvious. While this only applies to the first few notes and then both themes diverge from one another, a lot of people consider this more than enough to call "lazy" on Kajiura, and to consider the theme yet another reason to mock the anime.note To be fair, Kajiura has a bit of a reputation among her detractors of repeating herself too much in many of her other soundtracks too, both before and after her work on SAO.
Fuscus the Vacant Colossus. When it starts out, players can't even hit the damn thing without putting themselves at risk, since they need to step on what are essentially landmines that will force Fuscus to try grabbing or stomping on them. When when it's head appears, it will apply a Damage-Increasing Debuff on all players, which can put even dedicated Tanks at risk. It's later revealed that, since it's hiding within the Boss Room's surfaces, it can pop up from anywhere to attack, something Shivata learns the hard way when he's almost eaten by it when the group is trying to retreat, and the group can't immediately save him since he's able to move his weakpoint. Not helping matters is, as Kirito points out after the fact, it probably wasn't designed but more than two parties in mind, meaning that if it wasn't for Kirito and his improvised raid party, a bunch of players may have lost their lives.
The Irrational Cube was already hinted to be a torturous fight in the Beta as the Irritating Cube, due to it being a Rubix Cube of all things, it ends up becoming worse in the main game. While it operates just like a rubix cube, it's sides are changed from colors to match to sudoku puzzles, meaning that you not only need to solve the puzzles on each side, but you also need to move them in place like you would a rubix cubes' colors, meaning you could solve a puzzle on one side only to undo it because another side's puzzle isn't solved. Oh, and the door out is locked by it's own series of Sudoku puzzles, that are hard and numerous enough to take a pair of advanced NPCs an hour to solve.
The Fatal Scythe, which borderlines on being a Hopeless Boss Fight. It took off half the HP of both Kirito and Asuna in one hit. Kirito estimates that it could be of an equivalent level to the 90th Floor Bosses. It was only defeated by Yui using admin privileges to delete it.
The Skull Reaper, which could One-Hit Kill players and causing 24 casualties before being defeated. It took Kirito and Asuna's combined efforts to merely block its scythes alongside every other player flanking it to bring it down.
Technically speaking, Kayaba as Heathcliff is this and likely would have become this if the game went on longer. Not only does he possess a Unique Skill which gives him major Defense boost and allows him to use his shield as a weapon, something other shield users apparently can't do, but as the game's creator he has knowledge of every single Sword Skill in the game, meaning that most techniques, even those of other Unique Skills like Dual Wielding, are things he can counter easily and, as shown by Kirito, can easily bite his opponents in the ass if they activate one by instinct.
The infamous episode 10 of the Alicization saga. Aniplex USA decided to censor a rape scene zooming and cutting those parts altogether. No matters worse is that Aniplex put a warning message before the episode. Fans in America, Nordics and France are not happy about that.
Many Light Novel readers have complained about how PoH's backstory was altered in the anime, the main complaint being about how his time as a hitman for the Korean Mafia sent into SAO to kill a target was Adapted Out, and that he instead stole a Nerve Gear and logged in when he was bored one day.
The final stretch of Alicization in general got plenty of criticism from source material readers of changing and omitting details and scenes from the light novels for no apparent reason, particularly a significant amount of intimate moments between Kirito and Asuna and altering scenes with Alice in the real world that make her look closer to Kirito.
They Wasted a Perfectly Good Plot: This is one of, if not the most recurrent criticism the series receives from its detractors. Most people agree the premise is extremely powerful and full of possibilities, but Kawahara never cames close to realize that potential. On the broad strokes, they see the execution underwhelming due to crucial plot contrivances, questionable story choices and underdeveloped characters (See They Wasted a Perfectly Good Character above). Another huge point of contention is that, rather than exploring his otherwise good concepts, Kawahara seems to unabashedly focus on Pandering to the Base and Wish Fulfillment to a degree that detractors find alienating at best, and intellectually offensive at worst.
Kirito's Zero-Approval Gambit as a Beater in Episode 2 had a lot of plot potential and one of the more interesting directions his character was taken in, but it promptly gets dropped by the next episode where a Time Skip shows he's gotten sick of being a solo player and joins a guild, abandoning the characterization that had established in the previous episode. This gets resolved in Progressive which shows what happened during the Time Skip and Kirito keeps up the Beater act for far longer and leads him to be ostracized by nearly all players, who consider him a powerful asset to the Assault Team but almost no one trusts him on a personal level.
Another case due to Kirito. One of the main appeals of the series was the fact it was a death game set in virtual reality, where characters could supposedly die at any time. However this is mitigated by the fact that the story focuses on Kirito, who is an Invincible Hero where it's made apparent there is no true chance of him dying in SAO.
The biggest example would be not exploring all 100 Floors of Aincrad, instead stopping at Floor 75 with the arc only spanning 14 episodes/ a few books rather than a whole season. The video game continuity amends this by featuring all 100 Floors, while Ordinal Scale has the characters being able to see what would have been on the 100th Floor which they face as a Final Boss. Progressive also makes amends by actually showing Kirito and Asuna's adventures during the venture up.
The Phantom Bullet arc featured Gun Gale Online, a sci-fi themed shooter, which was vastly different from the fantasy settings of the previous two games introduced. However the game's full premise remains largely unexplored, focusing almost entirely on the BoB tournament and Kirito facing the Big Bad. Fatal Bullet and Sword Art Online: Alternative Gun Gale Onlinealleviate this to a degree by fleshing GGO out and giving full exploration of what the game is like away from Kirito.
Yuuki Konno. So powerful that she completely dominated even Kirito, the World's Best Warrior of SAO. She was pretty much invincible in virtual world, but sadly not so much in the real world.
Eugeo is a skilled swordsman in his own right, with Kirito suspecting that he may one day surpass him. Despite this, he's tragically killed when he makes an attempt on Quinella's life after destroying her Sword Golem.
The Mother's Rosario arc is widely considered the best arc of the series, due to its heavy usage of Character Development, especially for Asuna, and extremely emotional story line. As a result, the feature film Ordinal Scale had a lot to live up to, as well as any subsequent arcs that follow.
Ordinal Scale itself was one of the most acclaimed anime films of 2017, which put a lot of expectations on the third season of Sword Art Online featuring the Alicization Arc.
For that matter, Alicization is this trope as well, being the arc that took up over 50% of the original story's overall content and was the Grand Finale of the web novelnote Seeing that Moon Cradle is also an extension of the arc, alongside establishing well loved characters like Eugeo, Alice and Quinella and giving Kirito some much appreciated development. Unital Ring has a lot to live up to.
In Episode 11 of Alicization: War of Underworld during the gathering ALO players, two characters who appear to be Eiji as a Spriggan or Imp and YUNA as a Navigation Pixie appear just as Lisbeth gives a speech to the gathered players to convince them to help.
Megan Peters has also criticized the series repeated use of Attempted Rape of female characters by the villains as a plot device to motivate the male heroes, saying that the women are "[left] to suffer for misogynistic silence".
Unintentionally Sympathetic: Asuna's mother in the Rosario arc is portrayed as being out of touch with the way the post Aincrad incident world has been, and being too stuck up about her daughter's future, with her even taking a jab at Kirito for not being a good possible partner. While she is rather cold to Asuna, and Asuna has a completely fair point about her mother being distant from her, she comes across as fairly reasonable given the circumstances. For starters, her concern over Asuna's future is justified; Asuna was just trapped in a video game for nearly three years, something that resulted in her needing months of time to recover from physically, so Asuna's focus on playing games comes across as rather irresponsible for someone like that, which Asuna does understand. Her comments about the school Asuna attends also has a fair basis: the school is basically a place to watch survivors of the Aincrad incident and barely even counts as a real school, something again Asuna concedes is fair. Even her jab at Kirito has some basis in being understandable; Kirito is just a random boy Asuna met in Aincrad, and the fact Asuna is so dedicated to him at her age is unappealing from an adult's perspective, especially since her mother can't reasonably understand her feelings since she wasn't there. However, the fact that Asuna paints her negatively for all these, because it prevents her from playing with her friends, comes across as her being a bit more childish than intended.
While he's not exactly disliked by those around him, Klein is often shown to be the No Respect Guy among the main cast that the others like poking fun of because his bouts of immaturity and for being a Casanova Wannabe. However, he's also an Ensemble Dark Horse who everyone believes deserves more screentime and attention than he gets as is, with frequent demands that he gets some kind of spin-off for himself.
Sinon/Shino. Prior to meeting Kirito she had a Friendless Background and was ostracized and bullied by everyone around her for years. It isn't until after the Death Gun incident that she gets introduced into Kirito's social circle and finally finds true friends that make her happy. However among the fandom, Sinon is an undisputed fan-favorite and Breakout Character who has consistently smashed polls.
One of the main reasons why Kirito receives the Ron the Death Eater treatment by his detractors is the fact that he never tells any of the girls that he already has a girlfriend, so they shouldn't even try to get together with him. Thus, they read this as Kirito deliberately "leading them in" so they fall for him and then "friend-zone them", or even "emotionally cheating on Asuna". However, this misses the crucial detail that, in Japanese society, being direct about negative topics is extremely frowned upon. You only are supposed to be direct as a (very) last resort, less you risk to be considered a rude personnote A lot of Westerners have an extremely hard time forming meaningful relationships with Japanese people, both personal and professional, because of this social norm. When you take this into account, Kirito is as direct as you can reasonably hope for, especially considering his age and social skills, thus why the narrative always makes clear that Kirito only has interest in Asuna using other means. Special mention to the scene in Alicization, where close to the ending, Kirito asks Alice if Asuna can join them to go back to the Underworld. By Japanese standards, that's as subtle as a brick to the nose, which partly explains why he's a bit flustered while saying it, and why Alice is clearly holding back her anger when she replies.
Sinon's treatment in the second series. The backstory goes that when she was eleven, she and her mother were caught up in the middle of a bank robbery and Sinon managed to kill the robber with his own gun. This would be traumatic enough on its own, but it's also shown that she's been stigmatized and ostracized by just about everyone for this, including her own mother, who mentally regressed due to the intensity of the incident. This even extends to the therapists who learned of the event, so she has a case of untreated PTSD so intense that a schoolyard bully can set off a panic attack simply by pointing a finger at her and saying "bang". American viewers on the whole, regardless of their own individual views on guns and gun control, found this treatment utterly nonsensical and downright cruel, with many pointing out that if something like this were to happen in the USA, Sinon would be considered a hero across the board. Even in several countries in Europe, many of which are far more in line with Japan than America in their attitudes about guns, she would almost universally have been seen as a victim who was just acting in self-defense and did nothing wrong, possibly even as a brave person whose actions are actually commendable. This mostly touches on child-adult relations in Japan, rather than what Americans typically assume is some sort of gun issue (which are admittedly intense in Japan - gun laws are so strict that a firearm costs more than a luxury car). In Japanese society, children are viewed as relatively innocent and dependent upon adults (which makes the events of SAO seem even harsher by Japanese standards). What is really at issue, is that to Japanese society, a child is thought to be incapable of killing - that Sinon is able seems to create the presumption that she has the mindset of a cold-blooded killer, and the fact that her actions were done in self-defense is irrelevant. Which does not excuse what happened to her, merely better explain it.
Vanilla Protagonist: Leaving his abilities and controversial Wish Fulfillment aspect aside, character-wise Kirito is largely considered to be this in the anime. All of the VR-geekery and existential philosophy that he has in the light novels is adapted out. This is also a big part of his lack of appeal for his detractors, specially since the story still focuses on him instead of giving more dedication to the more colorful supporting characters that normally would stand out next to him. Many fans agree that Sword Art Online would be a lot better if Kirito either wasn't in the story or wasn't The Protagonist.
What Do You Mean, It's Not for Kids?: The original light novel, manga, and anime caters to the seinen demographic, and despite the massive merchandising making it easily recognizable also likeable, pretty, and adorable main cast and supporting characters, most of the villains are really,really nasty. Also, the Alicization arc is Bloodier and Gorier (although if light novels are any indication, Unital Ring seems to be Lighter and Softer). The video game storyline is considerably tamer since it lacks the aforementioned nasty villains (and those who exist had their worst aspects toned down), but they have a lot of pillow talk scene (which is basically the T-rated counterpart of Mass Effect romance scenes) in every single game (except Memory Defrag and Integral Factor).
The Phantom Bullet arc breathed new life back into the series coming off the tail of the heavily despised Fairy Dance arc, with a new female lead who had a very appealing personality and a tragic backstory, while the premise of a shooter game was very refreshing from the fantasy elements that the series had been known for.
For those not won over by the Phantom Bullet arc, the Mother's Rosario arc certainly did this. It received acclaim due to the intense emotional journey it takes viewers on and improving Asuna as a character.
Sword Art Online: Progressive, which is a re-imaging of the Aincrad arc, easily the most iconic arc of the series. It greatly fleshes it out by showing what happened on each floor (without any major Time Skips) and slowly developing Kirito and Asuna's relationship so their eventual getting together makes more sense. It also features more ongoing plots rather than collections of short stories like the original light novels. Even many haters and critics of the series are interested in an anime adaptation of Progressive.
Ordinal Scale did this for a lot of fans by addressing several issues that had been brought up over the years, an original story which had not been explored before by the light novels, and overall better handling of characters than the anime had done.
The Alicization arc is held highly among light novel fans and often considered the best written arc Kawahara has done for this series. Featuring the most creative storyline the series has explored, it touches upon philosophical implications of what it means to be human, raising the stakes back to being Trapped in Another World and fighting for ones life, genuinely terrifying villains, and the introductions of Eugeo and Alice. The anime adaptation followed suit and is by far the most praised arc of the entire series. Even the fiercest of SAO critics have begrudingly admitted it's a huge improvement and can even pass for being good (which, considering how viscerally these people hate the series and everything it stands for, it's one hell of a statement).
Though ironically despite being well received among those who only watched the anime, it ended up becoming a case of Hype Backlash among light novel readers due to the anime cutting content, notably the Zakkaria Tournament which only received a five minute flashback in Episode 7.
In the Calibur arc, as Kirito proudly tells the other members of the group to be thankful for the long set of stairs providing them a shortcut to Jotunheim, Sinon snarks at him for acting like he built those stairs. In the original, he says "Thanks for the tsukkomi" before pulling her tail, a reference to a primarily Japanese comedy routine. In the dub, Sinon calls him "a pain in the ass," whereupon he says "I've got your pain in the ass right here," and grabs her tail.
After Suguha becomes a main character in the cast, in the Japanese version, she will typically refer to Kirito as "onii-chan", a common affectionate term for "brother". All other characters call him Kirito. There isn't really a direct translation of the term that doesn't come across as an obvious translation, so in the English dub, she instead is the only character who exclusively calls him by his real name, Kazuto, instead of his in-game nickname, which serves the purpose of conveying a familial familiarity.
In the Alicization arc, Alice is surprised to hear Fanatio, who'd used a helmet to hide her gender, talking in a feminine tone. The localization of the light novel instead has Fanatio making a friendly greeting to Alice, even though they don't exactly get along.
WTH, Costuming Department?: Among his designs, Kirito's initial ALO Avatar from Fairy Dance is arguably his least popular, likely in part due to his sudden case of Anime Hair and the ridiculous size of his new sword. Some even derisively compare it to Cloud Strife. It's hinted that Reki acknowledges this, changing his design by the time of the Calibur Arc to closer to resemble his SAO design, and poking fun at his hairstyle in The Day After by having Yui demand he get haircut due to it being uncomfortable to sit on.