Headmaster of Hogwarts throughout most of the Harry Potter series, it is safe to say that Dumbledore is the most powerful professor at Hogwarts. With his Elder wand, Dumbledore managed to get away both times he was threatened imprisonment at Azkaban. He could also duel Voldemort and hold his ground.
One reason for this is that its many professors are extremely powerful wizards who spent years perfecting their craft. By passing their knowledge to an entire generation of students, they helped create many witches and wizards that became more powerful than themselves.
Dumbledore might be the most powerful teacher in Hogwarts, but the most powerful brain belongs to Professor Minerva McGonagall of Transfiguration class. In fact, she's the "Hermione" of her generation, that is, the brightest witch/wizard of her age. Professor McGonagall is a treasure trove of knowledge.
Snape is likely superior in terms of Potion making, magics of the mind and Dark magic. McGonagall is however almost certainly superior in her chosen field of Transfiguration. It's hard to say who outclasses who overall. Snape has a wider range of abilities/interests while McGonagall is more of a specialist.
Her power and skills were such that even among her fellow highly brilliant faculty members, Minerva may very well have been the second most powerful and capable professor at Hogwarts, her command of magic surpassed only by Dumbledore himself, displayed not only by being the teacher who was chosen to represent the ...
Verdict: Snape Is the Stronger Wizard
McGonagall is surprisingly skilled in the Dark Arts but not on the same level as Snape. She's also most likely incapable of casting the Killing Curse, which puts her at a disadvantage.
As I said earlier, many Hogwarts professors are arguably more powerful than Voldemort. Minerva McGonagall is, without question, one of them. A true Gryffindor, McGonagall is afraid of nothing, least of all Death Eaters or the likes of Dolores Umbridge.
Lord Voldemort is one of the most feared and powerful wizards. He is known for his cunning and ruthlessness. Formerly known as Tom Marvolo Riddle, Lord Voldemort was the most formidable evil wizard in the entire universe.
Minerva McGonagall
To be fair, it was McGonagall, Horace Slughorn, and Kingsley Shacklebolt who dueled Voldemort at the same time. Sadly, he incapacitated all three of them after being enraged at the news of Bellatrix Lestrange's death.
It's fair to say that Dolores Umbridge is the most-hated character in the Harry Potter series. Her blind loyalty to the Ministry of Magic and her condescending attitude towards her students immediately made her the most unlikeable teacher in Hogwarts' long and complex history.
Transfiguration. 'Transfiguration is some of the most complex and dangerous magic you will learn at Hogwarts,' she said. 'Anyone messing around in my class will leave and not come back.
Dumbledore also said that Voldemort was probably the most brilliant student Hogwarts has ever seen. Although Voldemort remains highly accomplished and prodigious in skill, he is enormously lacking and highly inept in the most powerful magic, love.
In the film, Snape is forced to fight Professor McGonagall after Harry Potter reveals that he was the one that killed Professor Dumbledore (at Dumbledore's bidding, though at the time the fact was unknown). Interestingly, Snape defends himself against the witch – but doesn't actually fire back.
House-elves could perform magic beyond that of a wizard
Dobby frequently demonstrated himself to be immensely powerful, causing Lucius Malfoy himself to back down with just a point of his finger.
Godrick Gryffindor, one of the four founders of Hogwarts, and the owner of the legendary Sword of Gryffindor, was absolutely more powerful than Dumbledore— and it's a good thing he was, too, because Dumbledore wasn't around in Hogwarts' early days to keep Godrick's fellow founder Salazar Slytherin in check.
1 Voldemort – Harry Potter
He who should not be named makes the number one spot. Voldemort is known for his viciously evil nature. He has wiped out entire generations of Wizards for standing against him, and his power in the dark arts knows no equal.
The Killing Curse was created in the early Middle Ages by Dark witches and wizards. Primarily, the curse was used to quickly slay opponents during a duel.
Winner: Snape
The kind of versatility in magical abilities that Snape displayed was almost around the level of Albus Dumbledore and Voldemort, making him easily more powerful than the average wizard and even the members of the Order of the Phoenix and the Death Eaters.
Weaknesses. McGonagall is never portrayed as having any particular weaknesses. Her stern facade likely prevents anyone from getting close to her emotionally, with the possible exception of Dumbledore. We are led to believe that she prefers her solitude.