Naofumi's behavior, particularly early on, paints him in a light almost as bad as the other heroes at the same time, just more internal. He's willing to abuse the fact low level monsters can't dent him to carry them around and threaten shopkeepers. His internal thoughts about the people around him tend to be dismissive or angry. Probably the furthest he goes is the entire sequence up to purchasing Raphtalia: he's utterly pragmatic about that owning a slave would be useful, responds to being shown he can magically torture one with all but a "that seems useful, yes" and ultimately selects Raphtalia not because she's the best option for what he needed (a combat slave) but because she was female and he could fantasize about enslaving Myne AKA Malty who had backstabbed him not long before. One of his first concerns when the heroes are recruiting companions is that he'd like a cute, female companion to protect. With all of his other behavior, he begins to hover really close to the acceptable edge of a Chivalrous Pervert.
Explanation Point argues that Naofumi is written as the perfect capitalist hero of which Ayn Rand would be proud. When society fails him and tells him he's not worthy of getting what he needs, he takes it upon himself to gather allies, money and strength by any means available. Despite others decrying them as unfair or immoral, Naofumi's methods are all legitimate or at the very least honest, and by helping himself, his success directly or indirectly trickles down to helping other people who need it, such as sick villagers, Raphtalia or even the world itself. But EP argues that this really only works because Naofumi takes it upon himself not to hurt people or be excessively greedy. Even though he literally owns slaves who are physically incapable of disobeying and he possesses skills, services and goods which people would literally die if denied access to, he doesn't abuse this power or squeeze the innocent for every last drop he can get—which, EP argues, is the most unrealistic quality Naofumi possesses but still makes him a good escapist fantasy. Worth mentioning is that this is solely an interpretation of the anime, the Light Novel and Manga version of Naofumi is much, much different.
Motoyasu comes off as an overall jerk whos Distracted by the Sexy, and is clearly unaware of the type of person Malty is, but he does not know Malty and the King are lying about Naofumi. In fact, the lie was specifically constructed so that he and the other heroes would believe it. He genuinely believes Naofumi to be a rapist. The issue is that his ignorance easily crosses into Lethally Stupid territory, whereupon it doesn't matter if Motoyasu is tricked into doing the wrong thing, because it's his own fault that he is too easy to trick and too self-righteous to control himself.
Did Ren and Itsuki bust Motoyasu, Malty, and King Aultclay on the "duel" they rigged against Naofumi because they genuinely wanted to help him, or was the latter three's disgusting behavior towards him so insufferably arrogant, condescending, and antagonizing that they simply couldn't stomach watching any more?
Are Motoyasu, Itsuki, and Ren really as savvy with RPGs as they claim to be? Were the games they played prior to arriving in Melromarc glaringly unbalanced class-wise? Did jealousy and envy eventually factor in? They immediately dismissed Naofumi for possessing the defense-focused Legendary Shield, deeming it a "useless" weapon despite the Stone Wall archetype being viable, if not vital for drawing and tanking damage in order to keep their party alive. It doesn't help that their opinion of him doesn't change despite him and his party defeating the Soul Eater and the power-mad Pope, and they just write off his hard earned strength as "cheating" despite knowing he had no help from either them or the kingdom from the very start.
In the anime, was Naofumi and Raphtalia's decision to spare Idol an act of mercy, or did they know he wasn't going to change and that whole scene was them drawing out his true nature which they can use as evidence against Melromarc?
Naofumi's initial act in having Malty and the King be executed seems jarring and hypocritical since few episodes ago, he tried so hard in preventing Raphtalia to kill Idol? However, it's possible that Naofumi simply cares for Raphtalia and didn't want her to stain her hands. It's also likely that he intended to kill Idol in secret. It can also be argued that he was partially motivated by simply avoiding the potential issue of clearing his name after actually killing a nobleman.
After Malty and the King drag Naofumi's name through the mud and make his life a living hell, getting five consecutive chapters of their unadulterated public humiliation at the hands of the Queen—not the least of which involves her allowing Naofumi to legally change their names to "Bitch" and "Trash"—is a satisfying experience, to say the least.
The anime takes this a step further. Malty has a slave crest bound to her that prevents her from lying, and predictably, she gets shocked several times every time she does so, with the biggest shock (the one that knocks her on her ass) coming from the False Rape Accusation that began the entire story. To top it off, they change her adventurer's name from "Myne" to "Slut" (originally "Whore" in the Web Novel, but it has the same effect). Compared to the Web Novel, where the Queen gives Naofumi the idea of something different from the death penalty, this was all Naofumi's idea.
Even better! When Malty begs for Motoyasu to come and save her, what does he do? He turns the other cheek, literally, and wised up to her at least for now. The look on her face when he does this is priceless.
An In-Universe example in Chapter 344 of the web novel, where Naofumi personally witnesses Witch's execution via burning alive at the stake.
Medea Pideth Machina is a sadistic goddess and the ultimate manipulator behind all of the villains in the story, chiefest among them Malty, who is a fragment of her. Desiring ultimate power above all, Medea begins destroying 8 worlds to harness the energy of their inhabitants, all while using physical copies of herself to sow the seeds of distrust and chaos throughout the 8 worlds, simply because she enjoys hurting innocents. To compose herself an army, Medea revives and brainwashes the corpses of those killed through her machinations, with the psychopathic Tact being just one of her servants; Medea also has no care for this army, slaughtering them all when they fail her solely to hear them scream. In the end, Medea reveals her plans to extinguish all life in the universe one world at a time simply to boost her power level, before flying into a rage when beaten and simply trying to take down millions with her as she dies. A self-proclaimed sadist who committed her crimes for nothing but more power and always with glee, Medea was the root of every single evil in the story, something she proudly boasted of at every turn.
Raphtalia's former owner, named Idol Rabier in the anime, is a sadistic bigot towards demi-humans. After the first Wave of Calamity, he has a village of surviving demi-humans attacked, slaughtering the adults and enslaving the children. Rabier regularly tortured his slaves, causing several of them to die from his treatment of them. Seeking to kill the wanted Naofumi to look like a hero, Rabier tortures Van Reichnott to try and find Naofumi's location, and attempts to do the same to Princess Melty afterwards. Upon being cornered by Raphtalia, Rabier begs for his life to be spared; when Raphtalia grants this request in the anime, Rabier tries to kill her anyway. With the last of his strength, Rabier releases a monster sealed within the town and orders it to destroy everything in sight, willing to put countless lives at risk all to gain glory by killing Naofumi.
The King of Faubley is a grotesque pig of a man who abuses his position to gain new "playthings". Threatening other countries to send him women, the King is a Serial Rapist who takes brides to rape and torture them to death, a fate so horrible that many prospective brides opt for suicide if possible. Upon receiving them, he proceeds to "play" with them and have them healed to continue the fun, having 9,999 brides that he has raped and murdered. When even the evil Malty is sent to him, the hero Naofumi cannot even watch the horrific recording of what the king does to her, despite his hatred of Malty.
Ho Yay: Motoyasu and Naofumi in Spear Hero, dear lord. As this is a timeline with a much more innocent Naofumi and a much different Motoyasu (i.e. he can only see women as pigs from the get-go this time instead of at the end of his Trauma Conga Line), he becomes fiercely protective of Naofumi and seems to have quite the man crush on him. The 2019 April Fool's Day short story even throws a nod to this, as its heroine is an avid slash shipper specifically of Spear Hero's version of Motoyasu/Naofumi.
Idiot Plot: The other three heroes treat their situation as a game rather than a matter of life and death, never considering the possible ramifications of their actions and frequently causing more trouble than they solve, and in Motoyasu's case, never questioning the acts of Malty despite several instances of her true nature shining through (her interference in Naofumi's and Motoyasu's duel, her attempting to kill Melty after Naofumi "kidnapped" her). The idiocy of the other heroes causes much of the drama later on, but it can be quite absurd at the sheer lengths they go to in being idiots that it can detract a bit from the story at times.
Iwatani Naofumi is a college student who, after reading a mysterious book, gets unwillingly transported to a fantasy world as one of four heroes tasked with saving the world. As the Shield Hero, Naofumi dreamed of adventuring and having a harem. However, he soon after was looked down upon for the shield's lack of offensive power, and is outright demonized by the people of the country, leading him to be shunned wherever he goes. With no one to help him, Naofumi must find a way to complete his mission and finally return home. Unable to use anything else in battle, he finds himself having to fist fight against monsters. His low attack stats make even weak monsters take minutes to kill, while someone with a sword can cut them within two slashes. Naofumi had no party members until a girl offers to go with him, and he feels his luck turn around until she steals his clothes and all his money, then lies that he raped her. From then on, no one wanted anything to do with him, and his hero status is the only thing keeping him from being executed. This hit him so hard he can't even taste food anymore, and he cannot leave this world until all four heroes stop the calamity that hits it at regular intervals. All he could do is buy slaves who can fight for him on the battlefield, but to them he's like an older brother/father figure. Out of his shields, he has one that reflects attacks, but it erodes his soul with each use.
At a young age, Raphtalia's village was attacked by monsters that came from the very first Wave, and her parents and many villagers perished. She was captured afterwards by slavers, and spent a period of time living under one owner to the next. All treated her horribly. After a while, she was bought by a slaver, and kept with the rest of his slaves until she was finally purchased by Naofumi. From then on, she served as his right hand, fighting against the waves, using illusion magic as well as swordsmanship, in order to prevent a repeat of her past from happening to anyone else. She does her best to help and serve Naofumi, as well as be a benevolent sister figure among their younger allies.
Glass comes from a parallel world like Naofumi's group. Initially seen as antagonistic when she crosses swords with him and his party, it turns out that by 'invading' their world, she is really trying to save her own. Her people are besieged by calamities just like Melromarc and all the other countries. In her world, she's a Hero just like Naofumi, and her sworn duty is to protect that world over anything else. She respects and sympathizes with Naofumi, but she knows that he could obstruct her objective, and with millions of lives at risk, she cannot afford that. Her solution to stopping the calamity is killing off the Legendary Heroes of Raphtalia's world as a last-ditch effort and her home is already on the verge of collapse, with most of it's people already giving in. She also struggles with inner turmoil, and she tries to keep it under wraps, but everyone can tell how much she's breaking on the inside. Despite all that, Glass is resigned to do her worst in order to preserve whatever's left of her home world.
Captain America would like to have a word. note One of the reasons why Naofumi is so ostracized is due to the shield being seen as a useless weapon compared to the sword, spear, and bow. Fans are quick to point out Captain America, who is the most famous fictional character to use a shield to its full effectiveness.
Misaimed Fandom: A few fans and many detractors view the series as saying women are lying thieves and should not be believed due to Malty's rape accusations driving the beginning of the plot. This is the same mindset Naofumi goes through for a good while early on, and it's presented as an overly cynical and false one he needs to grow out of.
Moral Event Horizon: For King Melromarc, his entire treatment of the Shield Hero is seen as this In-Universe. It takes over 300 chapters and the deaths of several major characters for him to finally own up to it.
As for his daughter Malty, in addition to the betrayal of Naofumi that began the whole plot, it is stated in the light novel that she crossed this long ago when she made the same false rape accusations on other men before Naofumi, and they didn't have the immunity to the death penalty that he did, making her not only a serial liar and manipulator but a Serial Killer.
Narm: The otherwise serious and intense trial in episode 21 of the anime is somewhat made less serious and more comedic by the choice of placing Male Gaze on Malty thanks to the Queen putting a slave brand on her chest to get the truth from her. What are supposed to be serious moments are hard to take seriously when the anime makes it look vaguely erotic. There's also a moment near the end of the episode where Malty gets hit with Gainaxing, except its right as she is putting put down to be executed. The moment is brief but enough to garner a chuckle at what was, again, supposed to be serious drama.
No Such Thing as Bad Publicity: Let's face it, the main reason why most people have heard of Shield Hero in the first place is because of the scene where Naofumi gets falsely accused of rape.
One True Threesome: Or foursome. The Four Cardinal Heroes occasionally get paired together.
Self-Fanservice: The dearth of shirtless scenes lead to some fan art depicting the Four Cardinal Heroes as having a decent Heroic Build (usually justified by all the fighting they've been through).
Signature Scene: The scene where Naofumi renames Malty and King Melromac to Bitch/Slut and Trash respectively has been coming the whole first season.
Theme Pairing: Despite all the animosity between them, The Four Cardinal Heroes get shipped together. To be fair, virtually all of the previous generations of the The Four Cardinal Heroes are implied to have been on good terms, with Naofumi's generation being something of an anomaly in that regard. It helps that unlike Motoyasu, Itsuki and Ren are somewhat less problematic to deal with directly.note This is most often among Japanese fans.
The removal of Naofumi's Kick the Dog moments and thoughts from the early part of the story has not been liked by fans of the light novel. The appeal of Naofumi early on in the light novel was that he was a Byronic Hero who despite being falsely accused of a crime, was still a flawed character who would do things like buy a slave to fight for him and even hope she gets hurt to feel satisfied at the thought of a woman being hurt to get back at Myne. The anime downplays almost all the elements that made him a firm Anti-Hero and instead paint him as a Jerk with a Heart of Gold who is just really grumpy. Since his thoughts can't be projected as well in the anime as well, a lot of Naofumi's internal thoughts and logic go unmentioned, and make him more cliche then he was initially supposed to be. The choice to have Naofumi be the one to argue in favor of sparing Malty and King Aultcray, whereas in the original story he wanted them executed but the Queen managed to calm him down and argue in favor of exiling them, was also very badly received by fans of the original series too, since it turned Naofumi into a good guy instead of a sympathetic but still harsh protagonist.
Episode 15 was criticized by those who read the Light Novel, for removing Raphtalia stabbing the noble and throwing him out the window, instead replacing it with her choosing to spare him (citing that she would become no better than him if she killed him), then the noble trying to attack Raphtalia, who retaliates by stabbing him with her magic sword, causing him to trip on the whip he dropped and fall out a window. Fans pointed out the flawed morality of the scene, as the noble had tortured and killed countless Demis before, and showed no sign of repenting, while his high-class status would make it unlikely that he'd actually face justice even if his crimes were exposed, meaning that his death at Raphtalia's hands would have been perfectly justified. While both versions do end up being the same in terms of outcome, it seems the change was made to avoid Raphtalia looking cruel since she is supposed to be a Morality Chain to Naofumi, but the change results in Raphtalia losing a moment of major development instead.
They Wasted a Perfectly Good Character: The party members of the other Heroes go unnamed and have almost no characterization or lines in the series. This is despite them being somewhat important given their supporting the various Heroes and have stakes in protecting the world. Excluding Malty, Motoyasu has one party member who gets named and plays a minor role, and none of Ren's party get any screen time or characterization besides being loyal to him before being all wiped out. The only party that has any significance is Itsuki's, and that's because they turn into antagonists later. While the series has a lot of characters, the lack of any time getting to know anything about them results in them coming across as odd given how much important stuff they end up being involved with.
They Wasted a Perfectly Good Plot: Having a party made of people from different versions of Earth could have been an interesting idea for an Isekai in of itself, however because the Legendary Weapons innately inhibit each other's experience gain when in close proximity, the heroes have to form their own independent parties from natives of the world they're now in.
Wangst: Naofumi's bitterness and cynicism can come across as this for some viewers who find him more of a Designated Hero due to his one-track mind.
What an Idiot!: Naofumi thinking the middle of a battlefield is a good place to start throwing out the "Reason You Suck" Speech. All he does is start a petty squabble among the Heroes when they should be focusing on the defeating the Pope and saving any moralizing speeches for afterward. The Pope is able to easily recharge his weapon without any opposition and notes how stupid it was for them to start fighting among themselves in the face of an enemy.