Malack. Exactly how evil he really is has been up for debate since the very beginning. How much he cared for his children, how much he does or does not genuinely respects Durkon, and a lot of other parts of his personality are up for debate. It was partly settled when Malack was revealed to be a vampire who planned an endless campaign of human sacrifice when he took over the kingdom, perhaps employing a special chamber. Then again, it was also made clear he did genuinely respect Durkon. He raised him as a vampire after all, and honored his last request to protect the Order of the Stick.
Does Tarquin really care for Elan as his son, or does he just think of him as a plot device? Given how dedicated Tarquin is to narrative tropes, a possible answer is both.
The Snarl, as a result of Epileptic Trees, has several. One notable one is that the planet within its realm is its effort to create life and an orderly world, unlike the chaotic nonsense which lead to its formation.
The Oracle is read by the majority fans as a simple Magnificent Bastard, but a subset of fanfic writers have taken to a rather tricky interpretation of the whole "Lickmyorangeballshalfling" thing. The theory goes that the Oracle, being totally omniscient and thus unable to be surprised by anything, is some kind of sociopath who manipulates people just to have some form of entertainment. After all, Belkar's prophecy was entirely self-fulfilling: he did end up "causing the death of" the Oracle (by, y'know... directly murdering him), but only after being goaded into doing so by the Oracle, who claimed that Miko's and Windstriker's deaths were indirectly his fault. The cyclic nature of the prophecy has been extrapolated by some to create a truly terrifying character that.... frankly doesn't really appear in the comic as such.
When the evil-aligned gods tell The Dark One about the Snarl. Was it just in their nature to do so? Was it a way to get at the heroic-aligned gods? Or, especially in Tiamat's case, are they also dissatisfied with the way the world is as their Patrons are XP-fodder much like the goblins?
Anvilicious: Strip #1068 has a female frost giant claiming she was holding back her true strength in the presence of some male giants, and could cut loose now those giants were dead. A lot of people on the forum thought that the delivery was ham-fisted, unnecessary, and downright insulting.
Arc Fatigue: Started to set in for some fans towards the end of Book 5 as Tarquin obsessively pursues the Order attempting to force Elan to follow the "correct" narrative structure. From his reappearance in comic #910, coming after the destruction of the Gate and a pointless battle with a monster summoned by Redcloak, there were a further 26 strips of this, released over 4 and a bit months, before they finally managed to shake him off.
And again with the Godsmoot meeting in Book 6, which got so vocal that Word of God eventually addressed it here.
Archive Panic: Over 1000 strips — and the "strips" are at least an A4 page's worth each, and sometimes more than one. In dead tree format, there are five books in print, plus two prequels, with another one nearly completed which will be longer than any of them.
Artist Disillusionment: Not total disillusionment, but interactions between the Giant and his fans can be rather surly, especially if he's being forced to explain himself to fans regarding plot holes, alignment concerns, and the creepy worship of certain characters, like Miko. Even things that might bear discussion get rather blunt shutdowns from the author.
Miko is a... polarizing character to say the least. Fans of the comic generally either love Miko or hate her. They started arguing about her back after being revealed at comic #200, and it's now over seven hundred strips later — and she's been dead since #464 — and no end in sight. (The author is not entirely happy about this.) And then there's those who Take a Third Option and love her as a character because they dislike her so much.
There is a bit of a divide among fans regarding how Word of the Giant states that Tarquin is not necessarily a Magnificent Bastard, and is more of a high-functioning / extremely lucky Big Bad Wannabe. Specifically the Giant's claim that we only had Tarquin's word for how awesome Tarquin was and that he hoped Genre Savvy fans would have picked up on this. For some, this was a welcome bit of canon and substantiated the implications they perceived that he was Wrong Genre Savvy, whereas others appreciated it because they viewed him as a borderline Villain Sue who needed to be knocked down a peg. Still others view this as spoiling one of their favorite villains, and claim it makes no sense with what Tarquin actually achieves in-story, citing how various unbiased characters have commented on how powerful and dangerous he is, the successful long-con on the Western Continent was his idea (unless that was a result of Unreliable Expositor too), and his demonstrable battle prowess against the Order. Another minor split along these lines is whether or not his tendency to adhere to story tropes means he's a strategic genius on a meta level, as he really is in a story, or whether it means he's severely hampered for when the story doesn't go the way he thinks it will, as the plot has outright defied several of these tropes in the past.
Belkar has always been one of the more divisive main characters but has become even more so in later strips with his 'fake' Character Development. Some fans welcome the possibility that he will be redeemed and possibly die a hero. Others are less thrilled, either because they prefer him as an amusing, completely amoral Chaotic EvilHeroic Comedic Sociopath or because they don't believe that any amount of good deeds can make up for the actions he's performed and therefore any redemption would be unearned.
In Book 6, Bandana and Andi, the acting captain and the chief engineer of the Mechane, both of whom are intensely polarizing characters. Bandana is the acting captain of the Mechane, and Andi (as well as some of the rest of the crew) don't take to her leadership well. Some readers insist that Bandana is reckless, incompetent, and egotistical, getting the ship into increasingly dangerous situations without adequately preparing for them, and trusting her crew to keep saving her bacon even as everything crumbles around her, and that Andi is the Only Sane Man desperately trying to take control of a bad situation to get the ship to safety. Others argue that Bandana is a skilled and capable captain, and Andi is a petty, egomaniac lunatic who seized the ship out of sheer jealous rage and then immediately delved into Commander Contrarian, proving why she shouldn't be in charge of the ship like she desires. And then, there are those who Take a Third Option and think neither woman has the talent to be a captain.
Sadly, like most stories of sufficiently lengthy length, The Order of the Stick has succumbed to this, with fans unsure whether they prefer the series pre-Cerebus Syndrome or post. Fortunately, most seem to be civil about this, but it has resulted in a few engaging in minor acts of Fan Dumb.
Creator Worship: The fanbase for Rich Burlew, a.k.a. the Giant. There are entire threads devoted to archiving his every word and all discussion or dissension on a storyline or plot element usually ceases as soon as he posts in a topic. (There's also the fact that he's the chief forum moderator and regularly locks threads which cross a fairly strict list of "banned" topics, such as "morally justified behavior" in the fictional world, real-world religion, and several others.)
In one early strip, Elan takes his clothes off and starts running around naked. Even Belkar is traumatized.
The Snarl's brutal murder of the Greek Pantheon... since you cannot normally kill the gods, and they helped create it.
In his attempts to get information out of O-chul, Redcloak threatens to throw a group of civilians off a tower and towards the Gate rift in the hopes that one of them will yell something relevant to their attempts to understand the Snarl... and throw another group off the other side "as a control".
Belkar. Thanks to his "fake character development", some insist he's Chaotic Neutral, despite Word of the Giant. Note that an early strip strongly implies that his constant anger and aggressivness is a consequence of his low Wisdom, being temporary wiser turns him into a non-violent nice guy.
In-universe, Tsukiko sees Xykon this way. Out of universe, he's a Love to Hate villain to the fandom.
Around the time Tarquin burned thirty escaped slaves alive as a present to Elan and some people argued he wasn't evil, and the person morally responsible for this was Haley for freeing them and "forcing" Tarquin to do this, it became apparent that Tarquin has a pair of pants so tight he had been sewn into them. Possibly because he looks like Elan.
Thog. Being lovably dim doesn't eliminate the fact that he's a brute and a bully who works with the bad guys.
After the reveal, Malack has gotten this. Despite the fact that he openly plans to sacrifice a thousand people per day to his god.
Thog, who was kept in the comic because of his unexpected popularity with fans. Which is lampshaded in the comic, naturally. It's worth mentioning that Rich Burlew also really likes Thog due to his endless potential for comedy; the Lampshading was simply him expressing confusion about how people felt the need to think he wasn't evil on the basis he was lovable (when in Burlew's mind, the two are not mutually exclusive).
O-Chul, aptly described as "everything right about paladins".
The "bandana paladin" also gets more than a few mentions here and there. His reappearance in the afterlife was noted with much excitement. It helps that he seemed to be on very good terms with O-Chul and died fighting his brethren that Xykon drove temporarily insane.
The Booted Wight, who unfortunately won't be appearing in the comic anymore.
The misspelling "Zykon the sorcerer" remains a bone of contention not just for the forums, but even in-universe for the dread lich himself, who can even spot his name being mangled in a speech bubble.
Other (traditional) examples in the forums: Hailie/Hayley/etc. for Haley, and Shinjo (portmanteau of Shojo and Hinjo).
In the Class and Level Geekery thread, bringing up certain questions that have been debated endlessly without anyone producing a satisfying answer. "How exactly did Tarquin catch those arrows", for example, has at least 3 possible explanations, all of which require either rule-bending or making assertions about off-panel events.
There's also an early strip where Durkon demonstrates the typical cleric reaction to the slightest hint that there may be any undead about. 860 strips later Durkon disliking the undead becomes a lot less funny.
In this strip V asks what the problem with binding someone's souls with dark magic is. Cut to a few hundred strips later, and a certain angry dragon...
When V describes his/her happy marriage, considering that it has now fallen apart.
He's Just Hiding: Some fans suspect Thog is still alive; the truth of the matter remains unclear, but the fact that they Never Found the Body and Rich Burlew declined to confirm his fate one way or the other lends fuel to the fire.
In On the Origin of PCs, one of the party members he tries to recruit is Buffy the Vampire Slayer. As it turns out, one of their foes does turn out to be a vampire... and he ends up being slain by another blond.
When Roy's dad is mocking him in the afterlife, he says, "Ooooo, yes! And while your friends collect the seven magic spheres to wish you back to life, you can train with the secret martial arts master who lives here in the afterlife!" Although it's a Dragon Ball Z reference, it doesn't change the fact that Roy learns a new feat from his grandfather while training with him in the afterlife.
In "Stopping for Direction", Belkar's observation that people who spend all their time cooped up in a hideout in the desert would probably head to a brothel first chance they get becomes even morespot-on when we learn that everyone who guarded Girard's Gate was family.
When Haley and Ian reunite in the Empire of Blood's prison, Ian says (while explaining why his plan to recruit fellow prisoners to his rebellion didn't work) that "smart people aren't cut out to be gladiators". Around forty strips later, Roy defeats Thog in the arena... using his smarts.
Loki caps off his speech to the Norse Pantheon with "Vote Loki 2016". This is now the title of an actual comic starring the Marvel version of Loki.
Strips #823 to #830: The "Team Evil getting ready to leave Gobbotopia" arc. It includes (within seven strips) the recovery of the phylactery by the resistance, the summary total annihilation of the resistance (save one member) and recovery of the phylactery by Team Evil, the outing of Redcloak's plan by Tsukiko and Tsukiko's subsequent (gruesome) death at Redcloak's hands. Holy Shit.
How about strips #868 through #879? Belkar meets Malack! Malack easily beats Belkar! Malack is a vampireand he just bit Belkar, intending to make more "children"! Oh wait, Durkon's here and he's actually fighing Malack on even terms — oh crap, Malack has a workaround for Mass Death Ward! And now he's bitten Durkon! Durkon's dead! And now Durkon is a vampire! The HSQ was raised dramatically by many of these strips being posted on subsequent days, which in contrast to the usual update schedule effectively turned the whole thing into a single feature-length Wham Episode.
#899 to #916: Xykon arrives just in time for the entire pyramid to explode, the Order glimpses the mysterious world through the broken gate, the Monster in the Darkness saves the Order from a premature final boss fight, a few strips to rest, then (in rapid fire) Malack's death, Durkon is no longer a Thrall, Zz'dtri's death, Durkon is working with the Order again, Redcloak's elemental is destroyed, Tarquin has brought one colossal army to the party and THEN, when everyone thought the shit had stopped hitting the fan, Tarquin kills Nale. THEN, as Tarquin seems hellbent on piling the HSQ on, he decides to order Elan's party dead on the spot to force him to become the main protagonist.
For a good time, mention Miko Miyazaki on the forums — or on This Very Wiki. This, despite how she's been dead for two thirds of the run of the comic. Reportedly, the Giant is disgusted.
Fans also began developing a hatedom for Haley's father Ian for his inaccurate assumptions on the Order of the Stick and his daughter's role in it.
Jerkass Dissonance: You could argue that Therkla was treated very sympathetically considering her actions. This is obviously meant as an example of Love Redeems, but she didn't exactly know Elan to any depth and on a closer reading it comes across more like "Unrequited Lust Somehow Redeems". She was happy to kill other Azurites or members of the Order unless he asked her not to, out of loyalty for an ambitious and clearly evil aristocrat. Wanting Elan to leave Haley to be with her wasn't a particularly noble motivation; one wonders if her attraction would be seen as more romantic or creepy if the genders were reversed.
Yukyuk when Belkar decides to get back at him for injuring Mr. Scruffy. Gross.
Nale spent most of the comic as an unrepentant mass-murderer. But the we get to meet his father, and realize what sort of childhood he must have had and how it formed him to the man he became, placing him in this trope. On the other hand, he is shown being cruel as a baby even when his parents were (presumably) together, so it's not all on Tarquin.
Miko Miyazaki is everything wrong with a paladin, but one of the bonus strips shows her trying to socialize with other paladins to celebrate New Year's only for her own Knight Templar tendencies to alienate them, forcing her to celebrate New Year's alone with Windstriker. It is implied this occurs every year. Miko's own zealousness causes her to be alone. Miko's subsequent fall from grace is also her own fault, but it means that when she dies, she is denied the only thing that still matters to her — being a paladin. Not to mention following on the heels of a nasty Broken Pedestal moment. At least she'll have the chance to see Windstriker again in the afterlife.
Thog. His mass-murder aside, the half-orc is little more than a child mentally and it's up for debate whether he even realizes he's evil. He thinks that he and the rest of the Linear Guild are friends having a big adventure, when really Nale and Sabine only keep him around because they need a frontline fighter and consider him a burden and an annoyance. The only mutually respectful relationship he has, not coincidentally, is with Elan. Even his final fate is left deliberately ambiguous.
The Oracle plans his resurrection spells in advance.
The three IFCC fiends play a longer game than anyone else on this list. For example, Deal with the Devil they offer V is so persuasive and tempting that V falls for it despite the existence of an alternative solution that didn't involve hellish dealing. They make use of it to great effect.
General Tarquin, who along with his confederates rules three desert empires from the shadows, playing them all against each other (and every group not aligned with their empires) with their patsies none the wiser. He is also Genre Savvy and thus is perfectly and explicitly aware of the costs and consequences of the role he has chosen to play in "the story" — he simply weighed the pros and cons, and saw that by his definition, he will "win" no matter what happens.
Xykon may be immature and unfocused, but he can be this. The best example is in Start of Darkness, when he manipulates Redcloak into murdering and reanimating his own brother (and thereby removing any hope of the goblins being free from him in the process), all to protect Xykon from an attack he was aware of and immune to anyway, and then delivers what may be the best "The Reason You Suck" Speech in webcomic history to explain that now he has guaranteed that Redcloak will loyally serve him forever, protect his phylactery, and perform any atrocious deed he commands. Because otherwise his sacrifice would be for nothing.
As of Strip #830, Redcloak solidified himself as this, by revealing that he's been manipulating Xykon for as long as he's been in "service" to him, revealed spectacularly with the following lines.
Redcloak: See, the undead are tools. Powerful, dangerous tools. From the lowliest zombie to Xykon himself, the undead are just complex weapons that we make and aim at other people. All that differs is how direct or subtle our control of them is. [...] for our so-called master, more creative strategies are required. Tsukiko:You don't control Xykon, he controls you! Redcloak: Like I said: subtle.
The High Priest of Hel, and by extension Hel herself is starting to be made into one. Acting as he's still the same old Durkon while secretly being The Mole to plunge the Dwarves into eternal torment? Good start for an Evil Plan. Becoming the Spanner in the Works for a meeting which will decide whether the wold will be destroyed or not? Score big points. Having their plans derailed by Roy and revealing they've made contingency plans beforehand? They graduated summa cum laude.
O-Chul. The fandom tends to treat him as the OotS answer to Chuck Norris. This is not unjustified, as it's been determined that he has a hitpoint total well over 150, putting him on par with creatures two size categories larger than himself. He's been immersed in a tank of acid for almost a full minute, escaping after being launched out by a shark-bite; he's tanked a disintegrate spell from Redcloak, followed by a Meteor Swarm from Xykon, without going down, and he beat Redcloak in a one-on-one fight while half-naked and with nothing but a metal bar.
Disturbingly, the times Xykon crosses it tend to be Moments of Awesome in that they are so evil you can't help but be impressed with which the style he pulls them off, even as you are appalled.
Miko crosses this when she takes the law into her own hands and kills Lord Shojo and the gods themselves take notice. By contrast, ''Start of Darkness' goes out of its way to demonstrate that there was never really a point where Xykon was not balls-out evil.
Nale crosses the line in the first story arc when he stabbed his brother Elan through the back simply for refusing to be part of his group (literally).
The end of Start of Darkness for Redcloak. Engineered by Xykon, who happily explains that he can now trust Redcloak to do any despicable action Xykon asks of Redcloak because otherwise he'd have to face that he crossed the horizon for nothing.
Xykon: You'll obey me forever now, because I give you an excuse for your inexcusable behavior.
Malack crosses it when he states his plans to continue Tarquin's empire... and kill 1000 people every day. And if that didn't convince you, he follows this up by killing Durkon and turning him into one of his children (though he states he will see him as a brother). Not to mention when he reveals that he killed his own seven brothers in the past.
Although his villainy was always horrific, it was generally played with some kind of humor, or at least some reader respect. However, Tarquin calmly telling Elan that he is going to murder Haley, then murder everyone else on the Mechane, then top it off by cuttingoff Elan's hand with a completely calm, straight face cements him as a monster at worst, and extremely frightening at best.
Golem Crystal cheerfully admits that she plans to go on a killing spree among the gnomes since killing helps her cope with the pain of her new form. She doesn't even consider Haley's suggestion to turn over a new leaf and go on a quest for an actual solution to her condition. In-universe, this convinces Haley that Crystal is an unrepentant murderer who needs to be destroyed.
Almost everything Malack said or did in the Empire of Blood arc comes back hard in the Girard's Gate arc, making re-reads way more shudder-inducing.
Ron the Death Eater: For a time, directed at Lord Shojo. Some of Miko's more die-hard fans claimed that executing him could be justified at first. The comic went on to show that no, it could not, and this went away rather quickly.
Saved by the Fans: Invoked by Word of God. Thog was originally going to be killed off, but the fans loved the big galoot so much that he rewrote the script and let him live. This wasn't done begrudgingly, though — at first, it was because there had been little to no major plans for the comic so it made little difference, but Burlew later admitted that he really liked Thog too, since he's a comedygoldmine.
The "Crack pairings" threads are among the most popular on the forums.
When O-Chul and new character Oona were revealed to be in the same geographical location (although they haven't met except in a single brief and inconclusive fight), out of nowhere came the new ship O-Choona, in a thread that ran for several weeks and will no doubt start up again as soon as either character reappears in a new strip.
Tarquin's banquet serves phoenix pâté. Since phoenixes explode when they die, the liver has to be cut out while the bird is alive.
As revenge for Yukyuk hurting Mr Scruffy (and to continue with his theme of utilizing kobolds' heads for various purposes), Belkar has Mr Scruffy use Yukyuk's mouth as a litterbox. While he's still alive. Bonus points for mentioning that "dairy just is NOT good for a cat's digestion".
Trapped by Mountain Lions: The frost giants arc, going on for close to a year, is veering into this. It basically amounts to a glorified random encounter and focuses heavily on side characters with very little character to them, despite the main characters supposedly being on a time-crunch to reach dwarf territory before the apocalyptic deadline. Numerous threads complaining about this have appeared on the forum only to be put down by locking. And unlike other side arcs or lulls in the storyline, it's not all that humorous and has virtually no Character Development to go around.
Unintentionally Unsympathetic: Celia and Haley have an argument over Belkar's murderous tendencies when he kills a nameless hobgoblin soldier and Solt Lorkyurg, an innocent gnome merchant. Celia feels that both murders were wrong and accuses Haley of falling under What Measure Is a Non-Human? by justifying the hobgoblin's death over Solt's, whilst Haley argues that the hobgoblin was an enemy soldier and not comparable. It's supposed to be one of the times the comic deconstructs common fantasy tropes and gives a balanced argument, but most fans sided with Haley's pragmatism and thought Celia was just being naive. Unlike other examples of What Measure Is a Mook? or Non-Human, this hobgoblin was an armed enemy soldier and part of the occupation of a conquered city instead of some random monster Belkar decided to pick on.
Unpopular Popular Character: Despite being a fan favorite, Belkar is disliked by 99% of the cast (the remaining one percent is composted of Lord Shojo, Mr. Scruffy and a female Greysky rogue he seduced). The fact that he's a Heroic Comedic Sociopath explains both reactions.
Tsukiko may have been smart enough to figure out Redcloak was lying to Xykon about the Gate ritual, but by bringing everything into the open, straight to Redcloak's face, she fatally underestimated the high priest of the Dark One.
If Nale thought his father was going to just let his killing of Malack slide, especially after he boasted about making the cleric suffer while dying straight to his face, he didn't know Tarquin at all, and deserved everything coming to him afterwards just for being that stupid. Even if Tarquin wouldn't have given him what he had coming, Laurin most definitely would have, making this doubly stupid.
Oh yes, Bozzok, call the flesh golem Crystal an idiot and do exactly what she was calling you on while you're totally and completely unarmed and have no way to defend yourself. See how long you last.