"You have now been marked with the Brand of Sacrifice. The lives of those who bear the Brand, from the last drop of blood, to the last moment of your agonizing death, will feed life to the new Child of Darkness."
― Void to the newly branded Band of the Hawk (Berserk)
This power grants the user enhanced/supernatural capabilities like strength, speed and/or the ability to manifest new appendages by the negative supernatural effect placed upon them which they can draw power from.
Akame (Akame Ga Kill!) using Murasame's trump card, "Little War Horn", to enhance herself via the blade's poisonous curse, but which will weaken and pain her for the rest of her life.
The Brand of Sacrifice (Berserk) marks those for a sacrificial ceremony in which an Apostle or God Hand is created...
...branded humans who survive reside in the Interstice between the physical and astral worlds, forced to fend themselves against creatures of darkness and the nightly attacks by the restless souls of the dead who desire flesh.
Jūgo (Naruto) in the process of mutating himself via his enzymes.
The crew of the Black Pearl (Pirates of the Caribbean)
Because of the curse of the Dark One, Rumpelstiltskin (Once Upon a Time) has an obvious in-human appearance, along with eternal youth and invulnerability
Imhotep (The Mummy) is a cursed existence by the power of Hom-Dai, an immortal spreader of the Ten Plagues of Egypt.
Ghost ÄRMs (Marchen Awakens Romance) are forbidden ÄRMs that fuse into and curse the user's body.