The world of BIONICLE is filled to the brim with characters, be they heroic, selfish, or just plain insane. However, despite the original target audience being children, BIONICLE has quite a few characters who stand out from the rest for being completely and totally wicked with no chance or desire for redemption, successfully disgusting all those around them by their sheer depravity.
- Makuta Teridax, the Big Bad, is responsible for orchestrating nearly all of the evil in the BIONICLE universe in his quest for godhood. Once a member of the peacekeeping yet vicious Brotherhood of Makuta, Teridax's campaign of evil began when, deciding he deserved to rule, he manipulated his fellow Makuta into betraying Mata Nui, infecting him with a virus that dragged him down from the heavens and sent shockwaves of destruction and anarchy throughout the cosmos. Following this, Teridax began waging war on anyone that wouldn't cow to his whims, with atrocities ranging everything from unleashing the genocidal Bohrok to kill thousands of innocents, to regularly trying to slaughter hundreds of Matoran. Even when seemingly beaten numerous times, Teridax always reaches out with his mind and corrupts other warlords like the Piraka into becoming his servants, using them to enslave and butcher entire villages alongside overrunning islands with the spider-like Visorak. Once gaining the god-like power he has so long craved by body-jacking Mata Nui's original form, Teridax annihilates his former allies while treating all life as playthings for him to torture and sadistically kill as he pleases. Teridax also subjects many rebels to horrific fates worse than death, and goes on to torture and brainwash the former heroes of the Matoran into becoming his personal attack dogs. In the end, Teridax tracks down a revived Mata Nui on the desert world Bara Magna, and attempts to obliterate the entire planet and its population just to spite his "brother". Teridax was a depraved, shockingly vile villain for a franchise originally meant for children, and stands out as the first wholly irredeemable villain in the setting, with his monstrous personality and 100,000 year campaign of darkness made all the worse by the fact that, as alternate reality versions of himself show, he was fully capable of redemption, yet rejected it at every turn.
- Makuta Mutran serves the Brotherhood of Makuta for the chance to perform his psychotic experiments unimpeded. Causing trouble even when the Brotherhood was more heroic, Mutran creates Matoran-devouring monstrosities and is known to have unleashed his beasts during the time of a civil war so as to cover up the death and destruction his creations wreak. Once gaining insight into the future and learning of Teridax's plans and the universe-wide destruction it will cause, Mutran doubles his efforts to get into Teridax's good graces and happily joins his revolution against Mata Nui, continuing his horrifying experiments in the process. Once developing the nightmarish Shadow Leeches, parasites that painfully devour all of the good out of their target, Mutran happily obliges Teridax's order to use them on an entire island, and thus rips out the morals of hundreds of Matoran, turning them into the Brotherhood's evil slaves. Wanting nothing more than to torture, experiment, and dissect all around him, what Mutran lacked in power he more than made up for in unbridled scientific sadism.
- The Shadowed One is the cruel head of the Dark Hunters, a shadowy organization of assassins and bounty hunters willing to do anything for profit. Ruling the Dark Hunters with an iron fist, the Shadowed One punishes minor slip-ups with torture and dismemberment, failure with death, and treachery with far worse than either. The Shadowed One uses the Dark Hunters to carry out countless acts of murder, slavery, and kidnapping, and, though many of the Hunters are just psychotic and greedy, some are forced into service by the Shadowed One when he threatens their lives or the lives of their loved ones. With no loyalty or true care to any but himself, the Shadowed One's Dragon lives a constantly tortured existence due to horrifying experiments the Shadowed One performed on him, while the Shadowed One's "closest ally", Ancient, is coldly executed by the Shadowed One to cover up a secret weapon of his own. By the end of the story, the Shadowed One has foregone all form of secrecy and subtlety to instead wage a war against the entire city of Metru Nui, and later attempts to harness the power of a lethal virus to blackmail any civilizations he wants with it. The Shadowed One is regarded as the most dangerous person in the universe alongside Makuta Teridax, and he does nothing to dissuade this proclamation.
- Roodaka is a treacherous manipulator who plays any and all potential allies for fools to get what she wants. With her powers of mutation, Roodaka makes a name for herself in both the Dark Hunters and the Brotherhood of Makuta due to her habit of mutating people into monstrous beasts to cow them into her service. Once becoming the Viceroy to Sidorak, king of the Visorak horde who she eventually betrays and leaves for dead, Roodaka uses her position to aide Teridax in wiping out entire islands of all life and turning any Toa who stand against her into mutated beasts just to mock them. Roodaka's biggest and most wicked plan is to release Teridax from his confinement, fully knowing the countless amounts of death and destruction he will cause, but uncaring as long as it asserts her dominance in the universe. One of the most self-serving villains in the BIONICLE universe, Roodaka truly cared for nothing and nobody besides herself and her own power.
- Pridak, known as "the Shark", was once the self-appointed ruler of the "League of Six Kingdoms", a villainous empire headed by himself and 5 other criminals, together known as the "Barraki". note As the leader of this League, Pridak organized the other Barraki to conquer nearly the entire Matoran Universe, slaughtering all those who aren't enslaved, with Pridak's own minions fairing no better, as he orders an entire battalion massacred simply because 3 of the over 50 soldiers in said battalion took a break. Though severely weakened after being locked away in the underwater prison the Pit, Pridak continues his plans for conquest, as he dismembers fellow Barraki if they question him, sics his pet sharks on Matoran, and forces another to watch as his city is ravaged by Pridak's forces. After escaping the Pit and ditching the other Barraki, Pridak tries to resume his insane plans for conquest, successfully wiping out a small island before being stopped. Pridak was the absolute worst the Barraki had to offer, and gleefully accepted this role in stride.
- Tuyet, a Toa of Water, is a fanatic who is obsessed with imposing her own "order" on the universe. While a nasty being who sadistically murders 3 Matoran to cover up a weapon she found in the "prime" Matoran Universe, it is in the Dark Mirror alternate universe where her evil shines. Having evaded capture for her Matoran serial killing by murdering Toa Lhikan, Tuyet uses the Nui Stone to convince other Toa to join together and create the "Toa Empire", a military ruling body that imposes their version of peace on the Matoran. Any Toa who stood against Tuyet were summarily brainwashed or executed, with the same fate befalling countless Matoran for the pettiest of infractions, with Tuyet ordering the liquidation of an entire tribe of Matoran solely because they have the ability to stand against her; one Matoran was frozen alive for walking too slowly. Along with covering the walls of her base with "trophies" ranging from weapons of fallen opponents to the opponents themselves, turned into living statues and decorations, Tuyet treats the Matoran as animals to be subjugated, going so far as to almost wipe out hundreds of them who rebel, only hesitating because it would leave her with less to lord over. With a final plan of conquering all other universes and turning then into totalitarian society she has created in her own, Tuyet was a terrifying example of a Toa's ability to take their "duty" way too far and become far worse than those monsters they claim to oppose.
- Metus is a slimy, treacherous Agori who sells out the entirety of Bara Magna to the Skrall for his own personal profit. His cowardly nature evident in the past when he ditched an entire group of his people to die to save his own skin, Metus later allies with the Skrall leader Tuma, offering him information on Agori village defenses and selling its defenders into slavery so the Skrall can wipe out the villages and either enslave or kill their inhabitants. After agreeing with Tuma that should anything happen to the Skrall leader Metus will assume command, Metus arranges for Tuma's death before taking control of the Skrall, planning to murder all those who know his true nature before conquering all of Bara Magna from the shadows. Despite his limited powers and abilities, Metus's evil is so wretched and his heart so black that Mata Nui compares his depravity to Makuta Teridax himself.
- Annona, from Sahmad's Tale, is one of the few villains to surface only after Teridax's defeat, and handily the worst. An ancient, dream-devouring entity, Annona drains entire civilizations of their dreams for empowerment, and the resulting lack of dreams drives the victims insane before they agonizingly die, something Annona drags out as long as possible so as to savor the taste of the dreams. After failing to drive the Great Beings themselves to madness to assert her dominance, Annona replenishes her strength by draining the Iron Tribe's dreams, leading to the annihilation of the Tribe, and later grants all females of the Skrall species with psionic abilities to watch as they wipe out the male Skralls for nothing but her own entertainment. Once awakening from her slumber, Annona enslaves the female Skralls for failing her, turning them into controlled puppets, then attempts to continue her spree of dream-devouring, even attempting to weasel her way out of a fight so as to feed on an entire planet. Treating her victims as nothing but "lunch", Annona was a purely evil monster who stands out as the only purely evil villain the Matoran encounter on Bara Magna.