Sometimes, it's not enough for an anime character to suffer a run-of-the-mill misfortune. In order to truly be a catalyst in a hero's story, the character has to go through something supernatural, like an evil spell. Anime curses provide rather tragic backstories and motivations for characters, and the curses' creators get really creative.
The worst anime curses usually involve death, like the Class 3-3 Curse in Another, which results in the gruesome demise of multiple people every year. Others are less violent but also quite harrowing; the Sohma Zodiac curse in Fruits Basket might seem cute and fun, but it leads to isolation, secrecy, and abuse.
A few of these awful curses do have a bright side, like how Sophie Hatter in Howl's Moving Castle learns a lot about herself after she rapidly ages from 19 to 90. No matter what form they take, curses can seriously spice up a story.
Another is a horror series about a lingering grudge that's besieged class Class 3-3 at Yomiyama North Middle School for decades. In 1972, a popular student named Misaki Yomiyama died tragically in a house fire. Rather than properly mourning his death, his peers decided to pretend he was still there. This triggered the Class 3-3 curse.
From then on, a dead person associated with the class is made into a new class member who's indistinguishable from the living. Since the dead person shouldn't be present on Earth, a string of deaths begin to occur. This cycle repeats itself each year.
One way the class tries to combat the curse (with some success) is to completely ignore one member of the class for a year. By pretending they don't exist, they create a sense of (tumultuous) balance the curse doesn't need to correct.
There are actually three curses in the Ancient Magus' Bride, and they're all different degrees of horrible.
The first two curses afflict Chise Hatori, a Sleigh Beggy. When properly trained, Sleigh Beggies can attract and control magic in abundance, but that magic gradually weakens their bodies, leaving them fragile and sickly. She later adds another curse to her repertoire when she tries to rescue a baby dragon from captivity and it attacks her out of fear. The dragon's curse – which will kill her – can't be removed without killing the dragon or being transferred to someone else, which Chise refuses to do.
The final curse belongs to Joseph, a 2000+ year-old being who became cursed with immortality after fusing with Cartaphilus, a man similarly cursed. Though he cannot die, his body can deteriorate, which causes him immense pain. In an attempt to either die or keep his flesh from rotting, Joseph performs gruesome experiments on other people.
The void operates like a miniature black hole, sucking in and shredding enemies with ease. However, there's a high chance the user will be sucked in, too—that's exactly what happened to Miroku's father.
The curse is passed down to the oldest male child in each generation of Miroku's family, which is why he's so gung-ho about having children. He wants to carry on the family mission to defeat Naraku, plus he wants to free himself of the curse. The only thing that can break the curse for good is killing Naraku.
When Griffin betrays the Band of the Hawk by trying to sacrifice them to achieve godlike powers, he leaves the survivors, Guts and Casca, with something called a Brand of Sacrifice.
This brand is essentially a curse that attracts demonic forces. Those with the brand can't stay in one place for too long or the area will become overrun with demons. They're forced into what feels like never-ending battle with demons of all kinds and they can never know peace. Even worse, the brand causes extreme pain and even bleeds when demons and other evil spirits appear.