Depressive Curse

"Voldemort, standing still, lifts his wand at [redacted], slowly as his followers [Death Eaters] stood in awe behind him. Shortly after [redacted] closes his eyes, Voldemort shouts like something stuck up in him: "Amouri Damnum!". A black light then jets through him and knocking him unconscious."

- Voldemort, inadvertently lifting the curse from [redacted]

The Breakup Curse (amori damnum) is a curse to end a relationship. Since 2015, it is an unforgivable curse.

Although the curse cannot be reversed, there are preventative measures one can take. For instance, one may dodge the black bolt, block it with a physical barrier, any living thing not a human or goblin, a magical creature, or by the use of Priori Incantatem. The Breakup Curse, just like the Killing Curse is considered 'unblockable', thus shield charms won't defend against it. If it hits something non-human, then a black cloud similar to which when a horcrux is destroyed will emit (when destroyed via the Sword of Gryffindor or the Basalisk Fang). If it hits a horcrux, however, it immediately destroys it. It is the only curse that destroys horcruxes on contact of a single black bolt.

Survivability
"People could in fact, survive this deadly curse. Although, the rate of which is severely slim, one could survive if prepared and responsible enough."

- Kingsley Shacklebolt's view of the Breakup Curse in the Daily Prophet

Chances of survival of the breakup curse is very slim. Unlike the Killing Curse, the Breakup Curse (is still fatal) is a slow and very depressing way to die if the effects are not treated at all or correctly.

Treatment and Health-Related Cases
There has been cases where witches and wizards have been cursed multiple times at once, putting them in a medically-induced breakup, and requires medical treatment, which are only available in wizarding hospitals like Saint Mungo's Hospital of Magical Maladies and Injuries.

Treatment Services for Muggles
Since St. Mungo's Hospital is not accepting Muggles (technically is no longer since the early 1690s), therefore, the curse is permanent and may inflict lifetime consequences, which is why the curse is unforgivable. But it can be treated through a series of blood tests and counseling and trained professionals, or admit to mental health based-hospitals like Spring Harbor

Notable Exceptions for Muggles
But Muggles can be accepted if any of the members from the Department of Health and Human Services gets consent with the Ministry of Magic. Unconsentual admission is prohibited and is a violation of the International Statue of Wizarding Secrecy.

Removal of the Curse's Effects
The treatment services are unreliable and can cause further damage. The only way to remove it is to be cursed again the second time, just as Christopher Lewis faced in order to defeat Lord Voldemort.

Withdrawals from the Curse
This curse does have side effects if not treated immediately. For instance, victims like Christopher Lewis had to suffer lifelong damages from the curse he got during his second year. The symptoms are very severe, and is likely to cause death. Each phase depends on the time you were under the cruse effects. The longer you wait for treatment, the more severe it will be.

Withdrawal Symptoms
These symptoms appear a week to one month after treatment, and usually wears off after six months to a year of that.

Etymology
The incantation, amouri damnum, is Latin for Love Loss, but damnum, closely related to damnare, which means damn. Either way, it either means love to be loss or love to be damned.

Trivia

 * In the Fifteen Reasons Why MMO/RPG, if you are hit by the curse, your max hp is set to 1% for 60 seconds while the curse is in it's preparation. During those 60 seconds, you are in combat. Teleport scrolls will not work, and logging out (by force-quitting, or by entering character selector menu) will kill you, but the curse will remain either way. The same goes for the Cruciatus, except your max hp is set to 25% and the Combat will end after only 10 seconds as opposed to 60 seconds. This makes (theoretically the) fourth curse extremely deadly if you are caught with it, since you are basically put down to a one hit kill entity, by any mob or player. Even a simple breakup when under the influence can kill you instantly.

Appearances

 * Fifteen Reasons Why and the Triwizard Tournament (First appearance) 
 * Fifteen Reasons Why and the Triwizard Tournament (film)
 * Fifteen Reasons Why and the Order of the Phoenix
 * Fifteen Reasons Why and the Order of the Phoenix (film)
 * Fifteen Reasons Why and the Case of Christ (Appears in flashbacks) 
 * Fifteen Reasons Why and the Case of Christ (film) (Appears in flashbacks) 
 * Fifteen Reasons Why and the Lost Love
 * Fifteen Reasons Why and the Lost Love (film)
 * Fifteen Reasons Why and the Crimes of Crouch
 * Fifteen Reasons Why and the Crimes of Crouch: Part 1
 * Fifteen Reasons Why and the Crimes of Crouch: Part 2