Monster / Sonic the Hedgehog
Dark Enerjak. Notice what's behind him.

Robotnik: Snively, what color is my heart?
Snively: I don't see a heart, sir...
Robotnik: Exactly.

Sonic the Hedgehog, though usually a lighthearted franchise, becomes much darker when these characters show up.

Video Games

Comic Books
  • Sonic the Comic:
    • Emperor Metallix is the supreme leader of the Brotherhood of Metallix and one of the comic's most significant early villains. Going rogue from his intended purpose as one of Robotnik's drones, Emperor Metallix begins a crusade to wipe out all life from Mobius and replace it all with machinery. To this end, Metallix forcibly duplicates the Omni-viewer, callously ordering his double agent Nack the Weasel killed when he sells out the Chaotix before trying to terminate the Chaotix themselves. Metallix later drives a crusade to roboticize the Miracle Planet—enlisting Grimer's unwilling help and later threatening to kill Grimer before Sonic's eyes—and, succeeding at that, alters history so that Robotnik never comes into being and Emperor Metallix leads a successful assault on Mobius that leads to the death of most of the planet's organic life and the few survivors relegated underground. Emperor Metallix has no compunction brutally killing whatever stands in the way to it and its own victory, and even Dr. Robotnik rightfully fears and dreads what Emperor Metallix is capable of.
    • Dr. Zachary, Knuckles's Arch-Enemy, is introduced as a seemingly harmless old man and one of the last of the echidnas. Zachary tricked Knuckles into leading him into the Emerald Chamber, whereupon he shattered the Master Emerald and used the Chaos Emeralds to empower a reprogrammed machine of his. Zachary gleefully allowed the inhabited floating island to fall onto Mobius as a "monument to his genius", intending to butcher the population of the planet Mobius for his own amusement before seeking revenge on Knuckles's people. In his second appearance, rebuilt as a cyborg, Zachary leads Robotnik to the location of the floating island's villagers so Robotnik could use them as components in a biological computer, which would consequentially kill them, a process which Zachary happily watched over. Possessed of a vindictive streak matched by few, Zachary manages to outshine most of the comic's other antagonists despite his relatively minor running as a villain.
    • Chaos, the Big Bad of the final arc, undergoes significant Adaptational Villainy from his game counterpart and becomes incredibly vile. Once a Drakon Prosecutor who fought for the glory of his cruel empire, Chaos was forcibly mutated into a beast made of Chaos Energy when he was exposed to the Chaos Emeralds. Sealed for a time, Chaos immediately goes on a destructive rampage once released by the careless exploit of Grimer, savagely killing Johnny Fleetfoot during his confrontation with the Freedom Fighters. Once Chaos comes into contact with the Chaos Emeralds again, Chaos attempts to drain them—uncaring this will cause the island they support to collapse into the ocean; even the amnesiac Super Sonic, who also used Chaos Energy, wasn't such an Omnicidal Maniac—and later successfully manages to achieve his Perfect Chaos form upon absorbing them in Robotnik's fortress, announcing his intent to remold the entire planet in his destructive image and murder all resistance towards him. In a comic already filled to the brim with villains that threaten all of Mobius, Chaos's actions have lasting effects on the Freedom Fighters and he ultimately stands as one of the most evil among the comic's villains.
  • Sonic the Comic – Online!:
    • In this Fan Web Comic that has received Approval of God, Dr. Zachary once again proves himself among the comic's nastiest. Zachary begins his new streak of evil by attempting to enslave Super Sonic to utilize his powers to wreak havoc across Mobius. Quickly cheated of that, Zachary builds up an alliance of like-minded psychopaths he calls The Syndicate and quickly builds a new plot to destroy Mobius utilizing the Chaos Emeralds. Snatching some of Sonic's DNA by capturing his young companion Tails and nearly drowning him, Zachary awakens the dormant Shadow the Hedgehog and uses his powers to draw the Chaos Emeralds out of the Special Zone, consequentially creating a massive chain reaction of Chaos Energy that obliterates the Special Zone and the billions of lives within. Brushing off the death of the Special Zone as a mere side effect of his plans, Zachary attempts to use a device he calls the Chaos Siphon to agitate the Chaos Energy on Mobius to the point where it causes an explosion potent enough to destroy the planet. Eventually foiled and captured by Knuckles, Zachary contents himself with sadistically mocking Knuckles about his failure to protect the Special Zone, and upon breaking out, forces Knuckles into a Sadistic Choice to either allow his friend Tikal to die or let the Floating Island collapse. A total sociopath as always who is utterly remorseless over the billions of lives lost to his machinations, Zachary proves he's no less of a monster here than he was in the original comic.
    • Vichama note  starts as an enigmatic flunky of Zachary enlisted in The Syndicate before revealing himself as something far worse. Vichama is in actuality the sadistic God of Death, an immortal entity who gained access to the physical plane through a deal with Pochacamac, using his new presence on Mobius to indiscriminately slaughter millions of echidnas. Trapping the souls of all of his murdered victims within his dark temple before he was banished, Vichama is brought back by Zachary and at first eagerly helps the doctor in his plot to destroy Mobius, helping to obliterate the Special Zone by proxy. Once Zachary's plot is foiled, Vichama leaves the doctor to die before rising his temple again and causing mass death through Mobius, assuming his true form as the God of Death. Casually incinerating Knuckles when he's confronted on his plot, Vichama announces his intent to bring the "gift of death" to everything that lives within the universe through all the enslaved souls in his thrall. Cloaking his murderous nature with a posh demeanor, Vichama is motivated by nothing less than a desire to spread mass death for its own sake and proves to be an utter bastard of a god who more than lives up to his title as the God of Death.
  • Archie Comics' Sonic the Hedgehog:
    • The original Dr. Ivo Robotnik, during the Great War, intended to test weapons he'd developed for the government on his own people and fled to the Mobians' side when he was to be punished for his actions. While acting as warlord for King Acorn, he secretly captured a peaceful village of Mobian monkeys and utilized them in an early attempt to create mechanical slaves by surgically implanting cybernetics, and of that entire village only one survived the process. Afterwards, he sabotaged the roboticizer developed by Charles Hedgehog just as it was to be used on his wounded brother Jules, making him think he'd turned his own brother into a mindless drone. When Jules's wife discovered the truth, Robotnik had Jules toss her into the Roboticizer and transformed into a robian as well, orphaning Sonic and crushing Charles's spirit to the point of retiring from being a Science Minister to running a chili dog stand. He then did similarly to Tails's father Amadeus on the day of his birth, making it seem as though Amadeus could care less for his newborn son and subsequently shattering his wife's heart, throughout which Robotnik maintained a straight face. Afterwards followed his betrayal of King Acorn and the takeover of Mobius, during which countless families were broken and millions enslaved, and over the course of a decade, he'd wreak havoc upon planet Mobius, destroying the ecology and pushing more than a few mobian breeds to the brink of extinction. And just prior to his death, he displayed a deeply disturbing relish at the thought of murdering one of his own kind and was positively gleeful when he got the chance to use his latest and greatest weapon on a fellow overlander.
    • General Kage Von Stryker is the leader of the Eggman-backed Dingo Regime. After ousting his father Helmut from power, Kage led his people in conquering Angel Island, imprisoning the Echidnas in what were clearly concentration camps, which led to countless deaths. He personally tortured Knuckles's father for the location of the Master Emerald, tried to wipe out the last echidna village on two occasions, and during the second attack boasted that he had crushed more Echidnas under his boot than he could remember. While like Helmut, Kage also hated the echidnas, unlike his father, Kage just wanted to Kill 'em All.
    • Dr. Finitevus was once a fellow scientist of a race of prosperous echidnas, until a freak accident changed his looks and intelligence. Despite his newfound genius, he was declared mentally unstable and was to be put down. He escaped and later sold out his home to Dr. Robotnik, resulting in everyone who had once lived there dying later. In addition, Finitevus manipulated four whole sides in a war—Dingoes, Echidnas, and two Dark Legion factions—into providing the fuel for the fire of his master plan, which is him deciding the world is hopelessly corrupt and wanting to purify fire. He, to this end, manipulated Dimitri, a head in a jar, into providing secrets and information, and then manipulated Knux into becoming Knuxerjak and starting a battle with his former friends after the whole corruption from power thing. Finitevus's expression at the scene where Knux becomes Enerjak shows he is not only mad, but completely delighted, even as his betrayed allies watch on and denounce him.
    • Hunter is a sociopathic Overlander known as a poacher of the Mobian kind. Hunter first debuts forcing Knuckles and his partner Monk into a hunt for their lives by threatening to murder Julie-Su, forcing the two to fight for their lives which ultimately leads to Monk's death. Though seemingly killed afterwards, Hunter is saved by Dr. Eggman and allows Hunter further work in his service, giving Hunter the chance to gleefully participate in Eggman's genocidal hunts and capture scores of innocent Mobians to have the life tortuously drained out of them in Eggman's Egg Grape Chambers, leading to the deaths of dozens. Proudly boasting of the various heads he keeps on his own wall of previous victims, Hunter's supposed sense of honor in his first appearance falls to reveal a sadistic mass murderer who hunts purely for the thrill of it.
    • Dark Enerjak, the tyrannical ruler of another dimension, is actually a version of Knuckles the Echidna, fueled by a desire to make the world a better place, whose Chaos Powers went out of control. While he started out noble, he gradually went more and more insane as time went on, before he considered everyone an enemy. Among his atrocities are the sinking of a continent; the destruction of several enemy cities, such as Station Square, as punishment for their defiance; and the capture of his strongest opponents and ripping their souls out—victims include Sonic, Shadow, Tails, Amy, Sally, and all the villains. He turns the souls into robotic slaves known as "Prelates". His soulmate was one of his victims, and he made sure not to use her soul to form a Prelate until the final battle, when he summoned her to fight their daughter, much to said daughter's disbelief. Dark Enerjak's mainly motivated by his own amusement, despite saying how much of a hero he is at other times. He allowed the Freedom Fighters to exist to give him something to do, sent soldiers to other dimensions to try and find new worlds to conquer, and continued to indulge Silver because of his power to actually give the living God a challenge. He derives joy from people's suffering, as seen with how he forces his own daughter to fight her mother and his former mate and how, upon seeing how upset Silver is at Enerjak using the souls to make his Prelate Army, he summons them all at once.

Sonic SatAM
  • Dr. Julian Robotnik is the absolute ruler of a roboticized Mobius, and is a far more chilling incarnation of the normally-bumbling character of Robotnik. A ruthless, ambitious backstabber with a series of treacherous moves to his count in the name of self-interest, Robotnik's first betrayal was his sealing of the wizard Naugus in the Void. Later becoming known to the King of Mobius, Robotnik became instrumental in the King's own military victories before deciding to take over Mobius himself. Staging a coup d'état and overthrowing the King from Mobotropolis, Robotnik stole the technologies of the Roboticizer from Charles Hedgehog, and used it to forcefully convert almost all of Mobius into a polluted dystopia. Reducing all of Mobius's inhabitants to his robotic slaveswhich they morally object to and fight against—Robotnik made fierce enemies with Charles's nephew Sonic and the rest of the Freedom Fighters. Robotnik would demonstrate his psychopathic nature again and again, attempting to kill, torture, or otherwise roboticize the Freedom Fighters, happily willing to jeopardize the ecosystem in doing so. Robotnik also coldly abuses his own minions, his diminutive, weak-willed nephew Snively among them, and condemns them all to die for the sake of his own life in the finale. An emotion-deficient fear-monger with nary a comedic quirk to his name, Robotnik proved one of the most vicious incarnations of Robotnik seen in the franchise.