Sylar (Heroes) had a "hunger" to gain so many powers, in-order to do that he had to kill his superhuman victims.
Angelus a.k.a "Angel" (Buffy the Vampire Slayer/Angel)is a vampire who killed people for entertainment.
The Mark of Cain (Supernatural) instills extreme bloodlust in the bearer
Corrupted by the Mark of Cain, Dean Winchester (Supernatural) becomes consumed with a murderous rage.
Warden Ray Carroll (Game of Silence) is the sadistic warden of Quitman Correctional Facility. Exploiting his power, many boys were systematically drugged, abused and even killed by Carroll and his staff.
During his berserk fits, Wolverine (Marvel) is lethal danger to all near him.
Zsasz (DC) had a desire to "liberate" people from their pointless existence.
After being driven insane by his own cybernetics, Cyber Shadow (The Young Guardians) became an unstoppable killing machine.
Being a vampire for Deacon Frost (Blade) meant killing humans.
The Predators (Predator/Aliens vs. Predator) are a race focused to hunting and killing.
The Boogeyman (Boogeyman film) is a monster who terrorizes and kills innocent.
Chucky (Child's Play) is a doll possessed by the soul of a man known as "The Lakeshore Strangler" for his mass murders.
Jason Voorhees (Friday the 13th) is a silent unstoppable killer who will slaughter anyone around him.
Roger Smith (American Dad!) brutally killing 24 prison guards to escape Bang Kwang Prison and using their corpses to build a boat.
Kei Munakata's (Medaka Box) Abnormality is his instinctive desire to kill. His instinctual ability as a killer is so great that he is capable of inflicting fatal injuries with his bare hands.
Akua Shuzen (Rosario + Vampire) giving her signature deranged look that is filled with killing intent.
Tyki Mikk (D.Gray-man) awakens, which drives him into a simple-minded in killing Exorcists.
Inuyasha (InuYasha), when overcome by his demon blood, has a tremendously murderous intent.
When taken over by his inner Hollow, Ichigo Kurosaki (Bleach) becomes a nigh-unstoppable killing machine.
Upon becoming a Super Saiyan 2, Gohan (Dragon Ball) became a merciless, sadistic killer who deliberately dragged out his fight with Cell to torture him.
Kid Buu (Dragon Ball) is a near-mindless killing machine who cares for nothing but wanton mass destruction. If he is not destroyed, Buu will not stop until everything in existence is wiped out.
While she has blue hair, Launch (Dragon Ball) is sweet and gentle. However whenever she sneezes, her hair turns blonde and Launch becomes a viscous psychopath.
Before being defeated by Naruto, Gaara (Naruto) was near psychotic killer, especially when Shukaku influences him.
Shukaku (Naruto) is a very bloodthirsty monster tanuki, and even more so when under the full moon.
Deranged with revenge, Sasuke Uchiha (Naruto) becomes a completely amoral murderer.
When his enzymes take over, Jugo (Naruto) becomes temporary insane with killing intent.
When Arlong (One Piece) is angry, he enters a killing mode of sort, befitting that of a shark.
Donquixote Doflamingo (One Piece) is one of the most sadistic characters of the series. Given his childhood trauma, swearing revenge against the mob, the Celestial Dragons, shooting his father and brother, his merciless attempts to kill Smoker, Law, Luffy, and the people of Dressrosa, and turning the citizens themselves against each other.
Caesar Clown (One Piece) is a mad scientist with a bad reputation for building weapons to murder people like test subjects. He even has no problem killing his own loyal henchmen just to demonstrate the use of his inventions.
Pica (One Piece) is very sensitive about his high-pitched voice. If someone so much as snickers, Pica will violently murder them.
Despite his flamboyant and flashy attitude, Dellinger (One Piece) becomes sadistic and bloodthirsty because of his own heritage of Fighting Fish fishman.
Gladius (One Piece) is feared for his very short temper which often gets the best of him. If someone offends him or his captain, Doflamingo in even the slightest way Gladius will use his powers to blow them up.
Caribou (One Piece) is an insane pirate known for slaughtering Marines. His sadistic nature leads to him using brutal ways to kill people such as burying them alive or suffocating them with his powers.
Cavendish (One Piece) possesses a dual personality, Hakuba, who is ruthless in slashing down everyone in range whenever Cavendish falls asleep.
Kaido (One Piece) is a ruthless warrior who does not make himself open to negotiation or excuses. Should someone fail to comply with his demands, Kaido won't hesitate to kill them. Kaido's crave for bloodshed has given him the idea of starting the biggest war in history.
Don Krieg (One Piece) is a ruthless pirate admiral known for his underhanded tactics and mass murders. His dishonesty and brutal nature earned him the alias "Foul Play Krieg".
Jack (One Piece) has an unreasonable nature and always resorts to bloodshed. During the attack in Zou, the Mink tribe told Jack they didn't have what he sought but he chose to fight anyway, killing innocent elders and children alike during his rampage.
Rob Lucci (One Piece) is a heartless mass murderer and the strongest member in the history of CP9. At the mere age of 13, Lucci slaughtered 500 kingdom soldiers for surrendering to pirates.
Thinking of himself as God because of his Logia Devil Fruit powers, Enel (One Piece) believes he has the right to kill anyone he wants and is one of the most sadistic, egotistical, and uncaring characters of the series. He even destroyed his entire home, Birkia just because he felt like it.
The Vinsmoke Family (One Piece) are a royal family of prestigious Underworld assassins.
Rei Ogami (Code:Breaker) ruthlessly killing evil while ignoring all pleas.
Giriko (Soul Eater) can overwhelm his opponents with sheer raw power of the blood-lust built up over 800 years.
Zahlenschwestern (Phantom of Inferno) are elite brainwashed female assassins of scythe master. They were created using the fighting data of ein,zwei and drei.
Zwei and Ein were taken by scythe master because of their natural killing instincts. They were brainwashed and trained to eliminate any threat to inferno. Zwei's eye color change when his killer instincts are activated.
Lucy (Elfen Lied) is the Diclonius meant killing humans, drove by DNA Voice.
As a creature born from evil energy, Orb (Marchen Awakens Romance) will kill anyone he wants without even a remote sense of remorse.
Despite his charms, Phantom (Marchen Awakens Romance) is the mad leader of the evil Chess Pieces army, who accepted the Zombie Tattoo to become immortal. Looking down on the mortality of the world, Phantom will stop at nothing to wipe out all of humanity.
Peta (Marchen Awakens Romance) shares Phantom’s ideals that humans are trash and feels no regret for the pain he causes others. He once even wiped out an entire fortress, not only killing enemy warriors, but innocent women and children as well.
After killing the ones who constantly bullied him as a child, Halloween (Marchen Awakens Romance) learned the pleasure of tormenting others. He grew up to join the Chess Pieces as one of their strongest and most sadistic soldiers.
After acquiring the power to get revenge on the men who tortured her, Chimera (Marchen Awakens Romance) decided to abandon her humanity as well as her original name, Eileen. From that day on, she would be known as Chimera, a monster who enjoys giving pain rather than receiving it.
Many plant manipulators, have the dream of growing a plant that will reach the sky. Weasel’s (Marchen Awakens Romance) Guardian ÄRM, Yggdrasil is a tree that grows bigger and stronger by absorbing the pain and suffering her master causes others. In order fufil his dream, Weasel will kill and torture as many people as possible to make Yggdrasil grow.
Candice (Marchen Awakens Romance) was a sadistic army commander who showed no mercy in battle. Her bloodlust only increased when she defected to join the evil Chess Pieces.
When Rapunzel and Girom’s (Marchen Awakens Romance) father died of a disease, their mother became demented. She denied them of everything, even food and whipped them each day. This abuse would later seep into the siblings giving them sadistic personalities.
Because of his ugly face, Kouga (Marchen Awakens Romance) has been treated miserably ever since he was a boy. The abuse and humiliation drove him into madness. Ever since he joined the Chess Pieces he's had a tendency to kill those around him, especially handsome boys.
Pinocchion (Marchen Awakens Romance) is a doll brought to life with dark magic. The evil nature of the magic inside him, makes Pinocchion an insane doll who will happily kill for his own sick pleasure.
Orco (Marchen Awakens Romance) is a simpleminded but sadistic Bishop class Chess Piece. He takes pleasure in destroying buildings and along with Girom, was the one who demolished the beautiful city of Vestry.
Maira (Marchen Awakens Romance) was once nothing but a cowardly Pawn-class Chess Piece. One day however he discovered Vaqua, a Guardian ÄRM with the power to absorb others. Since then, Maira has found pleasure in using Vaqua to absorb as many people as possible.
Maruss (Zatch Bell!) is a short tempered mamodo who finds pleasure in taking his anger out on innocent people. Due to Tia getting away from him so many times, he threatened that once he burned her book he would attack her bookkeeper's concert.
Zofis (Zatch Bell!) is a heartless mamodo who only cares about becoming king. After brainwashing the sweet Koko into becoming his sadistic bookkeeper, Zofis forced her to burn down her village.
Clear Note (Zatch Bell!) believes killing mamodo is the very reason for his birth and only wants to become king so he can bring genocide upon his people.
Assassin (Valkyrie Crusade)
Anki Master (Valkyrie Crusade)