User can place a curse on whatever they wish (people, places, objects, etc.). The exact effects can be nearly anything the user desires, ranging from minor annoyances to tortuously extended death.
Among the most common effects are misfortune/bad luck, various sicknesses, infertility, physical defects/ugliness, etc. when affecting people, breaking or working wrong or causing problems when used on objects and tendency to draw various disasters for places. Traditional magical curses include transforming the victim fully or partially into an animal/monster that fits the offense, blood-lust, insanity, unstoppable rages, unhealing wounds, misshapen/inhuman offspring, and a whole host of other effects.
The Cursing Camera (Doraemon) creates a voodoo doll of the person in the snapshot, basically cursing the victim to be at the complete mercy of the doll's holder.
Naraku (InuYasha) is well-versed in various curses and black magic…
…the most notable of which being the Wind Tunnel curse he placed on Miroku's family.
The forbidden Ghost ÄRMs (Marchen Awakens Romance) curse the user's body, turning them into a living weapon.
Using her dark magic, Diana (Marchen Awakens Romance) created and branded the Zombie Tattoo onto Phantom, giving him immortality.
Orochimaru (Naruto) can force his subordinates and subjects into mutation via a Cursed Seal.
Hidan's (Naruto) Jashin ritual will put anyone under his curse.
Est (Spirit Elementalist's Blade Dance) has her nickname "Demon Slayer" but is actually cursed demon sword that had absorbed those various curses and pass them onto its master, result in taking user's life.
Every Demon in Tartarus (Fairy Tail) can use Curses instead of Magic.
The house of where the Saeki family lives, Kayako (The Grudge) will curse them when the house is entered and will kill them, along with spreading the curse to anyone who comes into contact with the cursed ones.
Ingrid and Freya Beauchamp (Witches of East End) cursed to die young and be reborn to relive it again and again.
Anyone who has sex with Lee (Your Pretty Face Is Going To Hell) is cursed with elephantiatis of the nuts.