Akagi has no regard for his own life, can't be threatened, doesn't care about rules, will cheat if he can and generally doesn't really care about other human beings. He isn't really malevolent, however, unless you manage to piss him off.
Ana Satsujin has Rio Miyaichi, who is a mostly unrepentant serial killer and also our main character's new girlfriend. While she claims to only kill criminals, she also makes it clear that she's perfectly capable of killing anybody she feels like, and at one point randomly kills a police officer for no apparent reason aside from simply not liking his tone of voice while he was questioning her about another killer (while she herself wasn't under direct suspicion at the moment), and justifies her actions by saying that cops aren't people.
Though there's plenty of Ax-Crazy to go around in Baccano!, there is so far only one canonically confirmed sociopath is revealed in Children of the Bottle. Against all odds, this is not the unrepentantly callous Huey Laforet (who is capable of truly caring for a smallfew) or even the gleefully sadistic Fermet (who can understand and experience strong, genuine emotion), but rather the unrelentingly optimistic Elmer C. Albatross.
Due to a car accident and resulting brain damage, including some brain removal during multiple surgeries, Kazuo Kiriyama of Battle Royale cannot form meaningful connections to anything (a condition known as pseudopsychopathy in real life). The manga shows him mastering painting and the violin... and immediately throwing out both his artwork and his instrument when he's finished with them. He only associates with his "friends" because they won a coin toss; when they lose a second coin toss on the island, he slaughters them.
Interestingly, he is VERY self-aware that he is a sociopath. One of his lines, is that he sometimes gets 'confused' on right and wrong. When he slaughters his friends, he takes no pleasure in it. It is just something he has to do. Afterwards, however, he becomes a Determinator, dedicated to winning, with few lines.
Kazuo seems more of a Schizoid than an actual Sociopath. Sure he doesn't have a set moral compass but it's not because he doesn't like following the rules, he just doesn't care. He's never had a close friend (aside from his gang which he barely hung out with) and is completely indifferent to the circumstances surrounding him (such as when Mitsuko tried to flirt with him, but ended up getting herself killed instead.)
Despite somefan objection, this sums up Griffith. His high intelligence and charismatic and charming nature allows him to be quite ruthless behind closed doors, and he's fully aware of any line that he crosses so long as it brings him closer to his goal. Funny thing is that his counterpart, Guts, is himself a bit of a psychopath, but he has a working moral compass that prevents him from going that extra mile of no return.
Wyald is a far more low-functioning example than Griffith and Emperor Ganishka, as he is extremely impulsive and always pursuing instant gratification for himself with no respect for the lives or well-being of others, or even his own.
Thanks to the Black And Black Morality, all the villains they face also fall under this. Hell, even Ciel's staff, normally the Plucky Comic Relief, turn out to be this trope when we find out the real reason Ciel hired them was their combat skills making them practically one-man armies.
In the first couple of episodes of Black Cat many of Train's assigned targets seem to posses sociopathic traits.
Big Bad Creed Diskenth has many of the characteristics of Antisocial Personality Disorder; it hurts him rather than helping him as he is oblivious to his underlings' opinions of him.
Sosuke Aizen from Bleach. He puts on an affable façade, is themost manipulative character in the manga (with the possible exception of Kisuke Urahara), sees people as little more than pawns and tosses them aside once they've outlived their uselessness, harms people just because he can (just look at what he made Hitsugaya do to Momo), and tortured and killed who knows how many shinigami in order to create the Hogyoku, just so he could 'stand in Heaven'. He's responsible for the creation and near-execution of the Vizards, and came pretty close to destroying Soul Society itself. Mayuri has sociopathic tendencies as well, given the lengths he goes to in the name of 'research'.
Mayuri is definitely a sociopath. As his "evil-counterpart" on the villain's team, Szayel Apporo Granz, and quite a few other Arrancar, and by definition all normal Hollows. That some Arrancar aren't this is actually the remarkable part, but plenty of them aren't, even among the total bastards.
Nnoitra Jiruga and Kenpachi Zaraki also count.
Kenpachi is spared from being a total sociopath since he has at least three Morality Pets, including his adopted daughter Yachiru. If he were a true sociopath it's unlikely he would have bothered to spare her life, much less raise her and make her his squad lieutenant.
Incredibly, another contender has come along, with none of the Affably Evil of either, yet the A God Am I mentality of Aizen: Giriko Kutsuzawa. He kills his wife to test his ability.
Current Big Bad Yhwach is this. He treats everyone as pawns and as things to be replaced, seems to be warring against Soul Society since its there (not due to the old Quincy Genocide which probably a lot of his followers joined up to enact revenge for), reacts with zero emotion when he kills most of the 'impure' Quincy when his powers return, and doesn't care if the Vandenreich tears itself apart when he names Uryu Ishida as his successor.
Candy's bitchy step-sister Eliza Reagan in Candy Candy has several sociopathic traits. She's wholly selfish and incredibly manipulative, feels no shame in hurting others for her own gain or amusement, and believes she's entitled to get whatever she wants, by any means necessary. Never in the whole series does she ever show any sign of caring for anyone other than herself - even her Villainous Crush on Terence was less about caring for him, and more about wanting a hot guy all to herself.
Her brother Neil is no better - not only is he just as selfish and uncaring about hurting other people, but toward the end of the series, he develops a Villainous Crush on Candy, and it's just as shallow and selfish as Eliza's on Terence, not to mention obsessive to the point where he attempts to lock her in a house and never release her until she agreed to be his lover.
Lloyd Asplund cheerfully refers to himself as a sociopath. However, he could be considered a subversion since he actually lacks many of the symptoms of true sociopathy (Lack of Empathy, chronic lying, and narcissism); he's just very indifferent to all the fighting, manipulating, and killing that goes on around him, and all he really wants to do is fiddle around with the latest high-tech gizmos For Science!.
A true sociopathic character from the same anime is Brittanian knight Lucciano Bradley.
Prince Schneizel is an Affably Evil version. Lelouch points out towards the end of the show that Schneizel's inability to care about other people turns out to be his Achilles heel.
Vicious from Cowboy Bebop. Vicious is a cold, ruthless, bloodthirsty, and ambitious man who prefers solitude. He's Chronic Backstabbing Disorder incarnate, ungrateful to everyone, even if that person gave their life to save his ass. He's also willing to sacrifice anyone to further his own goals, weather it be his men, mentor, or even his loyal bird. The only thing he seems to really care about is power and revenge.
Darker Than Black: The Contractors are this through popular belief in-universe, but since they have all emotions missing or heavily subdued they don't just only have a Lack of Empathy but also lack the stimulation and self-worth aspects of true sociopathy. Although all their relationships are shallow like a sociopath's, Contractors don't seem to derive any pleasure from shallow affect and thus don't even bother acting 'normal' when not required to by the mission. It's also questionable whether or not Contractors truly have shallow affect, as a number of them do a number of irrational actions for the benefit of others. A number of Contractors (such as Wei, Genma and Ilya) show actual sociopath traits, but that seems to be limited to them personally.
Misa Amane, too. The histrionic kind. In one of her earliest appearances she's quite calmly contemplating how to kill Rem just because it would probably be more convenient. The fact that she fiercely and insanely pair-bonds to Light doesn't actually make her less of a psychopath, it just makes her one with poor self-esteem.
To the extent that he can be judged by human standards, the shinigami Ryuk fits a great deal of the criteria. He sets the plot of the series in motion when he deliberately drops his Death Note into the human world just to see the results, and when Light himself acquires the notebook, he makes it clear that if he doesn't provide entertainment through continuing to cause carnage and mischief, his own death won't be far behind. Light himself is eager to oblige for his own reasons, but while Ryuk sometimes expresses surprise at the depths Light will sink to, it's always with amusement or appreciation, never condemnation. Throughout the series, Ryuk never quite reaches Light's level of active evil, and in fact often serves as comic relief, but his role as an amoral eager observer is never obscured. In the end, he makes good on his promise to kill Light when he outlives his entertainment value, and despite Light's pleas, shows not a trace of remorse in doing so.
Hitoshi Demegawa, a scumbag TV executive who sees Light's killings as a chance to boost ratings, and eventually becomes the leader of Kira's cult and leads a riot against the SPK when he feels they're a threat to his new power.
Kyosuke Higuchi, who becomes the third Kira not out of any sense of justice, but to boost his own businesses. He's also a creepy scumbag who sexually harasses Misa.
However, it becomes clear that he isn't a complete sociopath when we learn about his past and realize that there is at least one person he cares for - Shinra. It's so extreme that he's more or less Yandere for him (though not in the romantic sense) to the point that he's stalking the man who hurt Shinra and setting him up for two huge crimes even though he realizes that he could get into trouble too. He even gets close to breaking down at the thought that he might have to betray his only friend to advance in his own goal.
Also, Izaya's never said that he is unable to love, just that he simply has no desire to.
Agon Kongo of Eyeshield 21 is this, along with having every single trait that characterizes antisocial personality disorder. Fortunately, with the series' scope being limited to high school football and a shonen jump title, most of his truly horrendous acts are stopped before they could follow through.
Solf J. Kimblee is a very nasty, low-functioning sociopath. He's only in the army for the chance to kill people, and takes it well beyond even the most Sociopathic Soldier. He doesn't even have any real loyalty in him; he just likes to hurt people. He had no qualms blowing anyone up, even innocent Ishbalan civilians. This extends to women and children.
Solf J. Kimblee is a high-functioning and very self-aware psychopath with a decidedly unusual worldview. For all his sadism and disregard for human lives, he does have some honor - largely based on honesty and duty and abides seriously by it and respects whoever fills these values; indeed, by the end, his own existence is expendable, and he prefers to distract Pride and subsequently have his own soul vanish than having to "live" inside of a hypocritical homunculus.
Father, a being who manipulated a king into destroying his own country so he could become immortal, then spent the next centuries creating a military dictatorship so that he could destroy that country to become God. He has no emotions because he cast them off into the Homunculi, and genuinely sees humans like they see ants.
The King of Xerxes, who was perfectly willing to go along with Father's plan to slaughter his people for immortality.
Barry the Chopper, a butcher who became a Serial Killer because he loved chopping meat that much, and saw his soul being bound into armour as an opportunity to kill more people.
Nakago in Fushigi Yuugi will go to any means to achieve his goal of godhood, and manipulates anyone who can advance his goals, and kills them when they are of no use to him. He manipulates Yui into making him a god, and knows that she would be eaten by Seiryuu afterwards, and kills one of the Seiryu warriors when he has no other need of him.
Goblin Slayer provides a remarkably textbook example that encompasses an entire race. The goblins are born without any empathy or ability to self-reflect; they do not, will not, and more importantly cannot recognize the pain they inflict on their victims. They see themselves as the superior race against common sense, and feed into that sense of superiority by degrading others through deception and assault. At the same time, they are blind as to why some people would hunt them down as a result, instead vowing to continue raping and murdering as revenge for something that was their own fault to begin with. Not that goblins need much more motivation anyway, because their short-term thinking and inability to delay gratification means they will almost never pursue anything beyond their destructive impulses. They don't even care for their own brethren, backstabbing and abuse being commonplace within their ranks. Most damningly, like any cornered sociopath they will default to cheap sympathy-ploys akin to slipping a mask on - there's no genuine sorrow present, just the hope that someone falls for their lies. The rank and file goblins act like low functioning sociopaths, while the smarter and more cunning classes of goblins act like high functioning ones.
Satou Matsuzaka shares several of the characteristics of a textbook sociopath such as her cleverness, manipulation tactics, and an artificial charisma to mask her true self. However, what prevents her from truly falling into this is her genuine love for Shio.
The Manager of the Princess Imperial has a bloated sense of importance, so much so, when Mitsuboshi asked Satou out on a date, she responded by kidnapping and raping him for a week as a way of rectifying that.
Asahi's father is a low functioning example of a sociopath who wastes no time with wasting the money he received from his inheritance to spend it on his hedonism. He lacks empathy for anyone he hurts, having raped his wife when they first met after she accidentally bumped into him.
The two thugs that nearly beat Asahi to death for no other reason than For the Evulz. After beating Mitsuboshi up, they decide to use Shio as bait to lure Asahi to the park so that they could resume beating him up.
Quite a few of the "targets" from Hell Girl portray sociopathic traits, most commonly by being almost unimaginably self-centered. A prime example would be a teenage baseball player who beats one of his teammates to death with a baseball bat and frames another for it...so he could get out of playing a game and putting strain on his shoulder.
The Major from Hellsing is a classic sociopath. The Major is charismatic, manipulative, and wickedly intelligent, even through his batshit insanity, but is simultaneously utterly bloodthirsty and utterly devoid of anything remotely resembling empathy.
Miki Kirishima from Hideout is a self-serving woman who paints herself as a grieving mother when her son died in an accident, but later displays disinterest in having another child and even coldly admits that she never wanted a son to begin with.
Azusa from Hot Gimmick. Some have said that Ryoki qualifies as one, but he seems to be more of a Borderline, or perhaps Narcissistic Personality. Hatsumi, meanwhile, seems to have some traits of Dependent Personality Disorder. Actually, most of the characters are probably diagnosable with some sort of mental illness or personality disorder.
While her behavior is usually Played for Laughs, Tabane Shinonono in Infinite Stratos shows several traits of a sociopath: she does things and takes decisions (including but not limited to aiding a terrorist organization threaten the safety of society) on the basis of how much fun she gets out of them, consequences be damned; she has a grandiose ego and a need for it to be constantly fed; she cares about no one that isn't herself or her right-hand woman Chloe (it is often shown that despite her upbeat attitude, she is a very hard person to like); and she can be very manipulativewhen she puts her mind to it. Although she does seem to care about her sister Houki (who rather understandably dislikes her), Chiyufu and Ichika, she also has no qualms about endangering them as her whims dictate.
Big Bad Naraku from InuYasha. As a conglomerate consciousness nothing about Naraku's psychology is normal, but he loves to manipulate people, play with their feelings and/or corrupt them, using them and later discarding them, without any remorse whatsoever.
Yoshikage Kira, who has an Ambiguous Disorder that gives him the drive to murder. He knows that killing people is wrong, but he sees it as a bad habit rather than an amoral crime. While he prefers not to fight, he does so out of a need to protect his own identity, and will not give his victims a peaceful death. As Kosaku Kawajiri, he scares, emotionally abuses, and outright kills his "son" Hayato, and he's brought back to life, he turns him into a literal Tyke Bomb so anyone who asks him for Kira's real identity will painfully die over and over.
And then there's Diavolo, whose introduction to Part 5 is dismembering a traitor to his gang, an act so gory the other traitor he had caught committed suicide. His defining trait is his extreme paranoia, preferring to run everything from the shadows and killing everyone that finds out his true identity. This trait is firmly established when it's revealed that he burned his hometown down, with the intent of being among the listed casualties. His other defining trait is his Lack of Empathy; he shows no remorse towards anyone, not even his split personality, and upon finding out he has a daughter, he has her sent to him with the intent of killing her, never mind the fact that, up until that point, she had no idea who he was.
Ragyo Kiryuin shows multiple signs of sociopathy, possessing an extreme sense of self worth and ego and a total lack of concern about her offspring to the point of sexually abusing her elder daughter Satsuki and literally throwing her younger daughter Ryuko away in the trash when the latter was an infant. She also ordered the death of her husband, casually sacrifices her employees and innocent bystanders to further her goals and outright rejects the concept of having empathy for anyone else. Her Leitmotif "Blumenkranz" outlines her thought process by comparing people to dead flowers that have to be trimmed without any remorse.
Nui Harime, as expected from someone who was raised solely by Ragyo. She loves nothing more than to murder everyone in sight, and considers all the hate she gets unconditional love.
Ryuko is briefly turned into a sociopath as a result of Ragyo brainwashing her. Her already fierce battling style is now driven by an Ax-Crazy personality, and she has no problems killing the ones she once considers friends, believing that they're trying to destroy what makes her happy. In short, an ideal daughter for Ragyo, just like Nui.
Let Dai: Dai doesn't understand empathy or why Jaehee cares about anyone other than Dai and himself.
Quattro from Magical Girl Lyrical Nanoha Strikers took great pleasure in torturing Vivio, called Dieci stupid for being bothered by it, manipulated Vivio into a fight to the death with her mother Nanoha, felt the need to taunt Nanoha, and spent most of the final battle calling her enemies and allies worthless. The only point she doesn't hit is a lack of attachment, since she's loyal to Jail.
Medaka Box: A lot of the characters are sociopaths to some degree (the title character narrowly escaped becoming one herself), but Ajimu takes the cake: not only does she regard people as things she's a Physical God. There's also Shiranui, who pitted her friends against an Irish wolfhound (a giant dog that was used to hunt wolves in Ireland) because it was funny.
Johan Liebert, the titular character from Monster. Any description of his sociopathy would become a plot summary.
Silas Edwards and Allen from Mother Keeper are both this, Silas buys slaves, drugs them and forces them to fight to the death for people's amusement. Allen was a part of this and kidnapped the person closest to one of Silas' slaves and forced them to fight to the death.
My Hero Academia: All For One carries all the traits of a classic sociopath: He has no empathy or remorse for all the things he has done, shamelessly bragging to his brother about how his followers had wiped out a faction of Quirk users who refused to join him. He views others as mere pawns to be used. He lies and manipulates others with ease. He's a Sadist who enjoys getting under other people's skin, often taunting All Might about the death of his mentor. He is incredibly arrogant and condescending to the point of megalomania and is charismatic enough to gain a loyal following of villains to serve under him. Even his taking in Tomura as his apprentice wasn't done out of altruism, but as a means of getting back at All Might by grooming Nana Shimura's grandson to be his successor.
All for One: [in response to a Heroic Sacrifice] Thank you for such wonderful comedy!
From Naruto we have Hidan, who unlike most characters in the series has no positive traits and never did. He slaughtered his village simply because he was disgusted with their pacifistic way of life, and performed gruesome rituals to attain immortality for himself. He's also Ax-Crazy and cruel for its own sake. On top of that, even the series itself seems to posit him as the most unsympathetic major villain, as he's exempt from the Cycle of RevengeAesop pervading the storyline with his Fate Worse than Death (though it helps Shikamaru's case that Hidan has nobody who would care about his cruel fate barring potential allies, and also that just killing him would be impossible).
Both ROOT and the Bloody Mist era of Kirigakure were dedicated into turning their shinobi into merciless killing machines without any emotions or who knew right from wrong. Sai, a member of ROOT who becomes a member of Team Kakashi claims the practice of killing the people closest to them is discontinued, but honestly struggles most of the story with dealing with emotions, figuring out what is right or wrong, and basic social interaction due to his training.
However, Danzo never truly discontinued the practice regardless of what Sai claimed. The boy just never underwent the final duel to the death because it's implied that his brother figure, who Sai was supposed to fight and kill eventually, had enough human decency that he decided to commit suicide instead of fighting Sai to the death to save his surrogate younger brother. Sai was essentially incomplete by Danzo's standards, and Danzo himself was entertaining getting rid of Sai after he no longer needed him because contact with Naruto and the others had compromised Sai in his eyes.
Hody Jones from One Piece; Fukaboshi's description of him fits the definition, as he's done many horrible things including revoking the prejudice of humans by assassinating the queen and blaming it on a human he had hired to work for him only to betray him and later taking over the kingdom and killing anyone who got in his way.
Three of the four Vinsmoke brothers the exception being Sanji definitely qualify. They have a severe Lack of Empathy, using their cloned soldiers as human shields and casually abusing servants. They're also almost completely emotionless, to the point at which when they, their sister and their father are about to be killed, they simply laugh and joke about it, not caring for their own lives or each other's.
Since it's a manga about pirates, One Piece is full of sociopaths. Kuro, Morgan, Krieg, Arlong, Eneru, Spandam, etc... It's actually harder to find a villainous character who's NOT a sociopath than one who is.
Tokugawa Harusada of Ooku: The Inner Chambers, in her childhood, regularly lied, framed her sister for theft, later pushed her to her death, and poisoned her own mother, all because she was bored. Since becoming mother of the shogun, she's poisoned a maid, gotten a senior councilor fired for not giving her a title, pitted her son's wife and concubines against each other, and killed her own grandchildren, all for her own amusement, and because the glory of sitting at the pinnacle of power wore off.
Shogo Makishima of Psycho-Pass is a charming, intelligent man who always has a bright white hue, even as he's slitting a girl's throat. Makishima also encourages other people to become serial killers and only views them as tools to be abandoned once they stop entertaining him.
Maria "Ai" Imari is a researcher who creates a strand of the Pupa Virus solely to impregnate herself with it so she could birth a monster. She suggests that Utsutsu become Yume's meal due to his regenerative abilities, but she otherwise expresses no concern if Yume were to transform into a monster and go on a ravenous rampage. She also remorselessly assimilates Yume to complete her goal.
Genjurou Imari was Maria's grandfather who had the tendency of adopting orphan boys and then savagely torturing them for his art. He also psychologically warps Shiro's mind into believing that such violence was love.
Shiro Onijima abuses his wife and children without restraint. However, he truly cares for his son and sees torturing him as his way of showing him affection.
Region: Takada sacrifices his students to the rats to save his own skin and later condemns hundreds of civilians to become rat food after his plan of disposing of his remaining student failed.
Revolutionary Girl Utena: Akio Ohtori has a superficial charm, which he uses to hide his despicable nature under the guise of a charming gentleman from the public. He manipulates everyone around him, including Anthy and Kanae, as pawns to regain his lost power as Prince Dios by any means necessary. He is a textbook Domestic Abuser to Anthy, passing her around like the prize to whoever wins the dueling game, raping her weekly, and telling her that only he can love her. He never accepts responsibility for Anthy's original death, her continued suffering, or his statutory rape of Utena; he instead puts the blame on both of them, the world, the townspeople, even claiming that Anthy willingly continued being a Silent Scapegoat for him and that Utena is guilty of sleeping with an engaged man.
Rosario + Vampire: Gyokuro Shuzen is completely incapable of caring about anyone but herself. Children by blood or adoption, lovers, subordinates... all of them are nothing but stepping stones to her and her quest for power and dominance.
While the visual novel version of Makoto Itou could change alignments based on player choices, the anime adaptation of School Days very firmly establishes him as a high-functioning sociopath. He has a need for stimulation that he satisfies by attracting and sleeping with his classmates, even though he's already in a relationship with Kotonoha. He has enough superficial charm and deceit to present himself as an upstanding student and Nice Guy as well as conceal his sleeping around. He shows no lasting regret for the damage he causes, save Kotonoha, and even then only when she's in his immediate presence.
Medusa from Soul Eater proves to be a Consummate Liar who doesn't care about anyone else and has a charming facade that allows her to infiltrate the DWMA as a school nurse without anyone suspecting her before revealing her true colors. She. Her child, Crona, gets the worst of it (with the dub even having her call Crona "it" because of another trope) and she once locked Crona up when s/he was little in a dark closet with no food for 5 days when s/he refused to kill 3 rabbits in 3 different ways and subjected him/her to horrific experiments to make him/her a Humanoid Abomination.
Kayaba Akihiko, the Big Bad of Aincrad, is a surprisingly realistic sociopath. He clearly has trouble seeing people as people, and he built his death game not because he wanted thousands of people to suffer, but simply because he wanted to build a world, and it wouldn't have been real if it wasn't populated. Nothing he does has any malice in it, and he played by the same rules as everyone else, always intending for the game to end with his death. Kirito especially slowly gains a grudging respect for him, if only because it's hard to hate someone like that.
A straighter example is Nobuyuki Sugou, Fairy Dance's Big Bad, wanting to perform inhumane mind control experiments on 300 SAO survivors, whom he openly describes as "guinea pigs" rather than people, and making an incapacitated Kirito watch as he tries to rape Asuna without a flicker of remorse. Sugou also has a grandiose sense of self-worth, declaring himself a god and believing that he's entitled to have Asuna despite the fact that she can't stand him, and unlike Kayaba, he's a vicious sadist who revels in his cruelty and evil. He's a high-functioning sociopath, hiding his true nature to Asuna's father by playing the part of a friendly, polite Honest Corporate Executive.
Vassago Casals/PoH is among the darker, more dangerous depictions of sociopathy. He is misanthropic, bloodthirsty, manipulative, and utterly devoted to dog-kicking. He establishes the Laughing Coffin guild so he can have people kill each other to satisfy his bloodlust, and even corrupts many an SAO player into player killers and even real-life serial killers.
Gabriel Miller, the final Big Bad of Alicization, is a classic sociopath, and the most dangerous example in the series. He is charismatic, manipulative, and wickedly intelligent, even through his batshit insanity, but is simultaneously utterly bloodthirsty and utterly devoid of anything remotely resembling empathy.
From Texhnolyze: the two main antagonists. Yoshii not only kickstarts a civil war in Lux, but murders a prostitute he had seemingly bonded and sympathized with the night before for no conceivable reason. Kano takes this trope and ramps it Up To Eleven, revealing in the final episode that not only does he have no problem forcefully turning a little girl into a cyborg, but that he doesn't even believe that anyone in Lux actually exists, let alone count as actual people.
Rize Kamishiro from Tokyo Ghoul appears to have been one. A beautiful young woman, she used charm and manipulation to lull victims into a sense of ease and then brutally killed them. Her appetite earned her the title "Binge Eater", for she frequently killed simply for the amusement while completely unconcerned about the consequences of her actions. Among Ghouls, she was infamous for moving into a Ward and throwing it into chaos with her sprees, then skipping town once her actions had brought in the authorities. If she had an ounce of empathy or compassion, she never showed it and stated she only cared about enjoying herself. Even other Ghouls found her selfish and cruel.
As well as completely disregarding human feelings, which doesn't really count since he hates them, he mindslaves his psychic 'sisters' into a giant million winged angel without really noticing they didn't want to, and torments his twin brother.
In Youjo Senki: Saga Of Tanya The Evil we have the titular character herself, who has virtually zero empathy for others and makes no acts of kindness that aren't meant to further her own career in some way; the few moral conflicts she has in the light novel have minimal impact on her actions and are cut entirely from the manga and anime. She casually sends upstart soldiers under her command to their death without a second thought, and tries using her childish demeanor to guilt trip and manipulate a captain into retiring early to eliminate him as a competitor. Everything she does comes back to her goal of climbing the ranks and landing herself in a safe rear-line position, and she never looks back on her actions with remorse. Interestingly, this and the fact that her mindset effectively comes from almost a century ahead of the setting also result in constant miscommunications and misinterpreting the actions of others.
Sakyou from Yu Yu Hakusho is a textbook example. As a child, he lived a normal life and had loving parents and siblings, but later got a job in a pet store, abusing and killing animals for the hell of it. Then he became a gambler, and then a crime lord, and by the time of the series, has plans to open a portal linking Demon World to the human realm just because "life would be more interesting" that way.
Even though Sakyo is still a sociopath, he remembers his happy childhood with a warm fondness, genuinely loved his family ("My parent were decent and kind people; it was what you could call an ideal family") and blamed nobody but himself for how he turned out. The English dub added a lot of changes to his narration, making him hate his parents and swearing he would kill himself if he became a white-collar worker.