The user can utilize the Black Arts: a form of magic typically used for selfish, self-serving and/or nefarious purposes. Though it is not necessarily "evil" magic, 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.
Demigra (Dragon Ball Xenoverse) using his dark magic on Piccolo, corrupting him and increasing his power level.
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 verisons 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.
Bowser (Super Mario)
Black Mage (Valkyrie Crusade)
Crowley (Valkyrie Crusade)
Dark Mage (Valkyrie Crusade) is a master of dark arts.