The Wizarding World is full of all kinds of magical characters, but some (such as Hagrid and Dobby) are just a little more skilled in their abilities than others. These individuals tend to be somewhat overpowered, demonstrating knowledge and magical skillsets that far outweigh their opponents'.
It would be unwise to duel with any of these highly powerful people, as being on the receiving end of their spells would be like receiving a Bludger to the face. Some of these characters have even demonstrated an ability to influence or deceive others, which makes them even more dangerous than your average witch or wizard.
Professor McGonagall
One of Hogwarts' most powerful teachers is Professor McGonagall. McGonagall is not only an Animagus - said to be one of the hardest skills to master - but she is also able to produce three Patronus charms at the same time, without uttering a single word.
During the Battle of Hogwarts, McGonagall also more than proved herself as a worthy opponent for the Death Eaters advancing on the castle. After taking down Professor Snape in a duel, McGonagall proceeded to bring the castle's suits of armor and statues to life, to assist in defending the school. Only a truly exceptional witch could pull off a huge feat like this.
Barty Crouch Jr
Using polyjuice potion to take on the appearance of Defence Against The Dark Arts teacher Mad Eye Moody, Barty Crouch Jr had everyone at Hogwarts fooled. Barty taught a highly complex trio of spells known as the 'Unforgivable Curses' - easily one of the greatest scenes set within a Hogwarts classroom - before proceeding to turn Draco Malfoy into a ferret as punishment for bad behavior.
Barty Crouch Jr even managed to trick Dumbledore into believing his lies, which is a testament not only to the strength of his polyjuice potion - already tricky to pull off - but also to the remarkable way he managed to deceive the supposedly foolproof Goblet of Fire into giving Harry's name, without Dumbledore ever suspecting a thing.
Sirius Black
Like Professor McGonnagal, Sirius is also an Animagus - although he achieved this feat at only fifteen years old. Sirius made a mutual agreement with his friends James Potter and Peter Pettigrew to master this skill in order to protect their friend Remus Lupin during a full moon, when he would transform into a werewolf.
Sirius was also partly responsible for the Marauder's Map, a magical object considered so dangerous that it was confiscated when Harry was later found using it in his third year. Whilst he was ultimately killed by Bellatrix Lestrange in Harry Potter And The Order Of The Phoenix, his legacy still lives on through his godson Harry, meaning his influence is still felt on the Wizarding community.
Lily Potter
As the mother of Harry Potter himself, Lily Potter ultimately helped set the events of the Harry Potter series in motion. James and Lily's relationship may have been tragically cut short by Voldemort's murderous ways, but Lily still managed to come out on top over the Dark Lord. Lily's refusal to step away from Harry at Voldemort's request created a sacrificial protection charm around The Boy Who Lived, causing Voldemort's killing curse to rebound.
It was Lily's love for her son which allowed Harry to live, and grow up to become the man who would eventually vanquish the Dark Lord. Lily's protection charm determined the fate of the entire Wizarding World; after all, there is no greater power in the universe than that of a parent's love for their child.
Delphini
Daughter of Voldemort, Cursed Child's Delphini's power comes not only from her magical ability but also from the way she is able to manipulate those around her. Delphini not only convinced Amos Diggory that she was his niece using a Confundus Charm, but she also used his confusion to coerce him into enquiring with Harry about using the Time Turner to bring his late son Cedric back.
Delphini's plan results in time being changed so that Voldemort wins the Battle of Hogwarts. Not only that but Delphini also mastered the Polyjuice Potion, which she then uses to disguise herself as Hermione Granger, and is even able to fly without the need of a broom - something that a very small number of people have been able to accomplish.
Harry Potter
Harry's reputation may largely stem from how he survived Voldemort's killing curse, but he is far more than a child who escaped certain death. He's also demonstrated a remarkable skillset from an early age, mastering broomstick flight in his first flying lesson, resulting in Harry becoming Hogwarts' youngest ever Quidditch player.
Harry also perfected the Patronus Charm in only his third year, and his magic capabilities allowed him to beat students significantly older than him in the Twiwizard Tournament. So impressive were Harry's abilities that he was encouraged by his fellow students to provide them with secret lessons, after being left unimpressed by their Defence Against The Dark Arts teacher Professor Umbridge.
Credence Barebone
Perhaps one of the most damaged characters within the Wizarding World, Fantastic Beasts' Credence's power is a product of a troubled childhood. Adopted as a child by the leader of an anti-witchcraft group, Credence found himself forced to suppress his magical abilities from his foster mother, who abused him for his differences.
This led to him developing an Obscurus - a manifestation of an individual's repressed magical abilities - and in turn becoming known as an 'Obscurial', the term used for those responsible for these manifested forms. Normally Obscurials die just before they reach the age of ten, however the sheer power of Credence's suppressed magical ability saw him live on into adulthood, which is clear proof that Credence is a formidable force.
Gellert Grindelwald
Before Voldemort came around, Grindelwald posed a significant threat to the Wizarding community. Not only did he demonstrate an immense amount of magical power, he also had a way with words, which saw him capable of radicalizing many magical personnel to his side - including one of Newt Scamander's most trusted allies, Queenie.
Grindelwald's spell-casting abilities went largely unrivaled, capable of conjuring projections of then-future events that he had successfully predicted such as World War II, and creating an extremely powerful charm called the 'Protego Diabolica', summoning a ring of fire that would only allow entry to those loyal to Grindelwald's cause.
Albus Dumbledore
Grindelwald's greatest enemy was Albus Dumbledore. Demonstrating some of the same strong magical skillsets, Dumbledore was able to perform elemental magic, as well as cast spells non-verbally, and even mastered many magical languages, such as Mermish and Parseltongue - the latter being a language very few can speak.
His greatest achievement was taking down Grindelwald in a duel, which brought about the end of the First Wizarding War. Dumbledore also proved a worthy opponent for Voldemort, assisting Harry in tracking down and destroying the Dark Lord's Horcruxes. Even after he was killed by Snape, he continued to play a key role in Voldemort's eventual defeat, appearing to Harry in a dream version of King's Cross with some strong words of advice.
Lord Voldemort
Also known as Tom Riddle, Lord Voldemort is easily one of the Wizarding World's most powerful wizards. At sixteen, Voldemort began the rare feat of splitting his soul into seven horcruxes, in a bid to prolong his life. In his fifth year, Tom opened the Chamber of Secrets, and managed to tame the basilisk inside.
Voldemort mastered many difficult spells, including all three Unforgivable Curses and various forms of elemental magic. He placed a jinx on Hogwarts' Defence Against The Dark Arts position which lasted many years, and even wielded the Elder Wand, which is said to be unbeatable. Voldemort ultimately perished at the hands of Harry Potter, but his spirit lives on inside his daughter Delphini, a true mark of an unstoppable force.