There's a spell for everything in the world of Harry Potter, from jinxes that prevent intruders from entering a property to healing spells that clear the throat of a choking victim. So vast is the range of spells in the magical world that the only tools witches and wizards need is a wand and their knowledge.
While most spells are used for the benefit of others or the greater good, there are spells that cause harm. Some spells are so dangerous that they're rarely used. However, with so many Death Eaters and other dark characters in the Harry Potter series, such spells aren't as uncommon as one would think.
Updated on January 16th, 2022 by Rhys McGinley: For audiences and hardcore Potterheads, the Wizarding World is a safe and magical place to delve into, with the movies providing such imagination and comfort for them. Not everything seen on-screen offers a sense of comfort, the cruel villains offer such evil and depth, and various spells and charms leave the jaws of fans dropped.
While there are all manner of relatively innocuous spells, as the Wizarding World is scrutinized and expanded, more and more incantations present themselves as wholly dangerous, lethal if used by the right (or wrong) Witch or Wizard.
Apparation
Apparition is the spell used by fully trained Wizards and Witches to disappear and reappear in another place instantaneously. It is one of the most magical forms of transportation seen in Potter films and books. However, it is also intensely dangerous.
Harry himself states that apparating is like being "forced through a very tight rubber tube," and the spell has disastrous results when botched. Audiences witness this when Ron gets splinched in The Deathly Hallows. Splinching occurs when the is not determined enough to get to their desired destination. Splinching could be minimal and not all that painful, but in the case of someone like Susan Bones, who lost her whole leg, it can be pretty awful and entirely dangerous.
Diminuendo
Diminuendo is a shrinking spell, which doesn't sound dangerous, but can be very effective in effectively disarming an opponent. In he Order of the Phoenix, it's used as a practicing spell on a Death Eater dummy of sorts.
In a real duel or battle, shrinking an opponent would render them almost powerless and much easier to defeat. Still, it's not as harmful as some other, more violent spells in the Potterverse.
Engorgio
The opposite of Diminuendo, Engorgio causes things to grow in size. It could be potentially devastating depending on what the caster uses this spell on.
Harry uses it to increase the size of a flame in The Deathly Hallows, which almost burns their tent down. It's an aggressive spell and highly effective, but and can create tools and weapons from anything in the caster's surroundings. It can also transform everyday objects into obstacles for enemies.
Confundus
This charm causes confusion, which doesn't sound so bad, but can be used to advantage in battles. Hermione uses Confundus on Cormac McLaggen during Quidditch tryouts in The Half-Blood Prince, doing this to help out Ron, a scene that clearly showcases the love between the two.
Cormac becomes disoriented and ends up making a fool of himself. In this instance, it's not dangerous, but in the heat of a duel, it could mean the difference between victory and loss - in some cases, serious injury or death.
Alarte Ascendare
Though it certainly wouldn't be pleasant to be on the receiving end of this spell, it's not the most dangerous in the world of Harry Potter. The only time it's seen in the films is during Harry and Malfoy's duel in The Chamber of Secrets.
When things get a little too intense, Lockhart intervenes in an attempt to show off his limited magical skills. He dispels the tension by throwing the snake conjured by Malfoy high into the air. Because it's a magical snake, it lands back on the ground unharmed. However, this could be a serious hindrance if used on another human.
The Unbreakable Vow
While not necessarily dangerous to execute, the Unbreakable Vow poses a threat to anyone brave enough to commit to it. Often used in dire circumstances, two parties must clasp hands under the watchful eye of a third party. The witness places the tip of their wand onto the linked hands. The vows are exchanged and agreed upon, sealing the bond. If either one breaks the Vow, they suffer instant death.
The Unbreakable Vow is seen in action in Harry Potter and the Half-Blood Prince, between Narcissa Malfoy and Severus Snape. Narcissa, wary of her son's involvement with the Dark Lord, makes Snape the Vow to protect and aid him. She also makes Snape promise that if her son fails, he will finish the task in Malfoy's stead.
Bombarda & Bombarda Maxima
Bombarda is a powerful piece of magic that essentially causes an explosion. When used with Maxima, the explosion is powerful enough to send anyone in the vicinity flying. Even without accentuating the effect, Bombarda is strong enough to break down brick walls.
Umbridge uses this violent spell to blast her way into the Room of Requirement in The Order of the Phoenix when she's hunting Dumbledore's Army.
Obliviate
Memory Modifying Charms are some of the most intriguing spells in the series, the standout being Obliviate. As a Memory Charm, it cannot cause physical harm to the victim. Its goal is to eradicate specific memories from one's mind. Since its creation by Mnemone Radford, its primary use comes from the Ministry of Magic's attempts at hiding aspects of the Wizarding World from Muggles. However, tampering with someone's memories may drastically alter their behavior. At worst, it can erase an entire life from existence.
In The Deathly Hallows, Hermione feels she has no choice but to erase herself from her parents' memories. With the threat of a new wizarding war looming, she's about to disappear for a prolonged period of time, and she's not sure she'll ever return. She believes she's keeping them safe by erasing their knowledge of the wizarding world. It will also save them from any emotional pain if Hermione is hurt or killed in the war.
Horcruxes
Surprisingly little is known of the Horcrux-making spell, though it's the most dangerous in the franchise. While most witches and wizards have no idea what the spell actually is, most know that one must first commit murder for it to work. This is an act so evil that it's believed to damage the soul, allowing it to be fractured. From this point, a witch or wizard takes a piece of their fractured soul and embeds it either into a person or an object, creating a nearly indestructible Horcrux.
Voldemort is the first person in history to divide his soul into multiple Horcruxes, essentially rendering himself immortal. As long as even one Horcrux remained, he could always return.
Stupefy
A commonly-used spell throughout the Harry Potter series, Stupefy is a crucial dueling spell for any witch or wizard to learn. This spell renders opponents unconscious without causing lasting damage, so while it's not the most dangerous spell, it is highly effective.
Since Aurors aren't allowed to use any of the three Unforgivable Curses, they often rely on Stupefy. This is seen in The Order of the Phoenix when of the Order battle Death Eaters in the Department of Mysteries.
