"The Dark Arts are many, varied, ever-changing, and eternal. Fighting them is like fighting a many-headed monster, which, each time a neck is severed, sprouts a head even fiercer and cleverer than before. You are fighting that which is unfixed, mutating, indestructible."
― Description of the Dark Arts by Professor Severus Snape to his students
The user can utilize the Dark Arts, dangerous system of techniques based around a darker side of magic that typically used for selfish, self-serving and/or nefarious purposes. Though it is not necessarily "evil" magic, dark arts tend to focus on destruction, harming, cursing and otherwise complicating the lives of other people while advancing the user's state.
Users often reject social convention and the status quo, which some suggest is in a search for spiritual freedom. As a part of this, they embrace magical techniques and practices that would traditionally be viewed as taboo and are generally willing to go farther than most would even consider if it serves their ends.
For fan-fictional to non-canon characters, see here.
Mozenrath (Aladdin: The Animated Series)
The Lich (Adventure Time) became an abomination through his abuse of the dark arts.
Hex (Ben 10 Series)
Charmcaster (Ben 10 Series) using a dark resurrection spell to bring her father back from the dead which requires all the living souls in Ledgerdomain...
Grail (DC Comics) is adept at using dark Amazonian magic to summon her father, Darkseid.
Raven (DC Comics/Teen Titans)
John Constantine (DC/Vertigo Comics)
Circe (DC Comics)
Enchantress (DC Comics)
Klarion the Witch Boy (DC Comics)
Black Adam (DC Comics)
Zatanna Zatara (DC Comics)
Maleficent (Disney’s Sleeping Beauty)
Queen Grimhilde (Disney’s Snow White and The Seven Dwarfs) is skilled in the Dark Arts
Viren (The Dragon Prince) is a master of Dark Magic.
Claudia (The Dragon Prince)
Amora the Enchantress (Marvel Comics)
Doctor Stephen Strange (Marvel Comics)
Morgan le Fay (Marvel Comics)
King Sombra (My Little Pony: Friendship is Magic) is a master of dark magic.
Princess Celestia (My Little Pony: Friendship is Magic) briefly using dark magic...
...and her student, Twilight Sparkle (My Little Pony: Friendship is Magic) manages to imitate the technique.
Eclipsa Butterfly (Star vs. the Forces of Evil) is infamous for her use of dark magic.
Moon Butterfly (Star vs. the Forces of Evil) cast the dark spell granted by Eclipsa.
Wuya (Xiaolin Showdown) powers are mostly derived from Heylin Dark Magic.
Trix (Winx Club)
Morgana (Tales of Arcadia) is a witch of dark magic.
The Dark Dragon (American Dragon: Jake Long) is a powerful evil dragon who possesses powerful Dark Magic that allows him to conjunct shadow dragons called the Shade Demons to battle other magical creatures or powerful dragons like Jake Long.
Lord Oberon of Avalon (Gargoyles)
Queen Tintania of Avalon (Gargoyles)
The Weird Sisters (Gargoyles)
The Magus (Gargoyles)
The Archmage (Gargoyles)
HIM (The Powerpuff Girls) is master at this type of magic
Skeleton King (Super Robot Monkey Team Hyper Force Go!)
The Sorcerer (Randy Cunningham: 9th Grade Ninja) has powerful dark magic thanks to his Chaos Pearls which he uses "Stank" powers to turn people into monsters when he senses their negative emotions, thus amplifying his powers.
Unlike typical Force users, the Nightsisters (Star Wars: The Clone Wars) wielded Magick that was connected to the Dark Side.
Zeref (Fairy Tail) is feared as the most powerful master of Dark Magic ever known in the history of wizardry.
Diana (Marchen Awakens Romance) is recognized as the most powerful dark witch in the entire world of MÄR.
Evangeline A.K. McDowell (Negima) cute, ain't she?
Medusa Gorgon (Soul Eater) wields dark magic in the form of snakes. All the Gorgon sisters have animal-themed dark magic.
Dark Magician (Yu-Gi-Oh!) using its signature attack, Dark Magic Attack.
Dark (Hardcore Leveling Warrior)
Pooh Upooh (Hardcore Leveling Warrior)
Darkist (Hardcore Leveling Warrior)
The Zogratis Siblings who makes the Dark Triad (Black Clover) are strong Mages who are hosts of three high-ranked Devils, which bolstered their natural magics, gained access to their devil's magic and malicous mana.
Wizard Howl (Howl's Moving Castle)
Demigra (Dragon Ball Xenoverse) using his dark magic on Piccolo, corrupting him and increasing his power level.
As Magical Zombies, the Fork Maidens (New Blood Interactive's DUSK) use Dark Magic to mainly fire bolts of magic at their victims and/or enemies. They also always have their own hands infused with it as well. However, it's unknown how far they can go in terms of using it.
After his fall from grace by the hands of Raiden and elder gods; Shinnok (Mortal Kombat) was banished to hell where he became ruler.
Ganondorf (Legend of Zelda series) is a skilled practitioner of dark magic, able to cast deadly curses, send the world into a state of endless night, create phantom versions of himself, project electric spheres of energy, freeze his foes with waves of darkness, as well other deadly abilities.
In addition to his combat abilities, General Tsao (Sly Cooper) is a master of black magic.
Bethony (Summoners War)
Bowser (Super Mario)
Black Mage (Valkyrie Crusade)
Crowley (Valkyrie Crusade)
Dark Mage (Valkyrie Crusade) is a master of dark arts.
The Charmed Ones (Charmed) were consumed with dark magic for a temporarily time...
...As Piper Halliwell (Charmed) was a Warlock, was able to encase a shapeshifted Zile in ice...
Prince Koura (The 7th Voyage of Sinbad) is said to be trained and skilled in every dark art known to man.
Nora Dhark (Arrowverse)
Willow Rosenberg/Dark Willow (Buffy the Vampire Slayer)
The Warlock (Harry Potter/The Warlock's Hairy Heart) practiced dark magic to avoid falling in love.
Tom Riddle/Lord Voldemort (Harry Potter) was known to be the most powerful and most wicked dark wizard of all time.
Death Eaters (Harry Potter) utilizing dark magic.
Harry Potter (Harry Potter) utilized in certain Dark Arts, such as the Unforgivable Cruciatus and Imperius Curses when he was against his hated enemies.
Like his late father, Morzan, Murtagh (Inheritance Cycle) uses dark magic, but because of his training with Galbatorix, Murtagh is even more powerful than his father was.
Nimue (Once Upon a Time) is the first original dark one that originated dark magic.
Queen Regina (Once Upon a Time)
Rumpelstiltskin (Once Upon a Time)
Maleficent (Once Upon a Time)
Emperor of the Night (Pinocchio and the Emperor of the Night)
Damien Darhk (Arrow)
King Kalakai (Pair of Kings) was the creator of the Dark Side of Kinkow before Zadoc and Katia.
As an evil sorcerer, Zadoc's (Pair of Kings) dark magic was able to bring the Dark Side of Kinkow to life, causing monster to rise and the land itself to turn evil.
Most of Kaita's (Pair of Kings) dark magic also come from the Bat Medallion, which allow him to control the Dark Side of Kinkow and summon dark creatures like zombies.
King Galbatorix (Inheritance Cycle) drove deeper into the dark arts after going mad with the loss of his dragon. He learned the horrible secrets of magic that should never be taught.
Fanoxean's (The Young Guardians) sheer strength in the Dark Arts can destroy entire dimensions.
Severus Snape (Harry Potter) had a passion for the Dark Arts from a young age, and was especially talented with curses even when he was still a student, Snape was already talented enough that he was capable of creating new dark spells, as most of the spells he created were curses, hexes, and jinxes and even served as a teacher of Defence Against the Dark Arts with his encyclopaedic understanding of the dark arts Snape taught the class to such an effect that even Harry Potter could not help but be enchanted by his knowledge.
Lord Voldemort (Harry Potter) was unbelievably talented and phenomenally accomplished in the Dark Arts at all levels, widely considered to be the most powerful practitioner of the Dark Arts the world had ever known during his reign of terror. He had a masterful knowledge of the most arcane and complex magic that wizardkind was capable of and could perform them successfully, such as the ability to create Horcruxes and raise an army of Inferi using necromancy and was also highly masterful in the use of all three Unforgivable Curses.