User can utilize the Dark Art: a form of magic typically used for selfish, self-serving and/or nefarious purposes. Though it is not necessarily "evil" magic per se, dark arts tend to focus toward destruction, harming, cursing and otherwise complicating the lives of other people while advancing the user's own 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.
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 verisons of himself, project electric spheres of energy, freeze his foes with waves of darkness, as well other deadly abilities.
Willow Rosenberg/Dark Willow (Buffy the Vampire Slayer)
Bowser (Super Mario)
Evangeline A.K. McDowell (Negima) cute, ain't she?
Fanoxean's (The Young Guardians) sheer strength in the Dark Arts can destroy entire dimensions.
Wuya (Xiaolin Showdown) Her powers are mostly derived from Heylin Dark Magic.
Tom Riddle or as he's most commonly known as, Lord Voldemort (Harry Potter) was known to be the most powerful and most wicked dark wizard of all time.
In addition to his combat abilities, General Tsao (Sly Cooper) is a master of black magic.
After his fall from grace by the hands of Raiden and elder gods; Shinnok (Mortal Kombat) was banished to hell where he became ruler.
Black Magician (Yu-Gi-Oh!) using its signature attack, Black Magic.
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)
Black Mage (Valkyrie Crusade)
Crowley (Valkyrie Crusade)
Dark Mage (Valkyrie Crusade) is a master of dark arts.
Dark Mystic (Valkyrie Crusade)
Raven (DC Comics)
King Sombra (My Little Pony: Friendship Is Magic)
Princess Celestia (My Little Pony: Friendship Is Magic)
Twilight Sparkle (My Little Pony: Friendship Is Magic)
Diana (Marchen Awakens Romance) is recognized as the most powerful dark witch in the entire world of MÄR.
Prince Koura (The 7th Voyage of Sinbad) is said to be trained and skilled in every dark art known to man.
Queen Grimhilde (Snow White and The Seven Dwarfs) is skilled in the Dark Arts
Demigra (Dragon Ball Xenoverse) using his dark magic on Piccolo, corrupting him and increasing his power level.
King Galbatorix (Inheritance Cycle)
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.