THIS STORY CONTAINS SPOILERS FOR Harry Potter books 1-7 and their movie adaptations.

SPOILER WARNING!

Hands-down, Albus Dumbledore was the most powerful wizard of his time. Dumbledore was a master of all major disciplines of magic, an inventor of his own spells and magical devices, and as a duelist, he defeated both Gellert Grindelwald and Voldemort in his lifetime.

Although he could definitely talk a big game, Gilderoy Lockhart's empty boasts brought about his eventual downfall. Filled with ambition, Lockhart lacked drive or tolerance for personal failure and ends up with a heaping pile of karma for his troubles.

Even though Lord Voldemort is not capable of challenging Dumbledore, he knew more about different realms of magic. Voldemort was also extremely adept at curses, was a Parseltongue, and the most accomplished Legilimens in history which allowed him to read, control, and break minds.

Severus Snape was a student prodigy who became an expert in all manners of magical disciplines. As a potions master, he could brew the most difficult potions, improve recipes, and his masterful ability came in handy when he invented a potion that saved Dumbledore's life after he encountered Voldemort's curse.

Although he was intelligent and bookish, Quirinus Quirrell was the weakest of the Hogwarts professors—mostly due to his extremely timid nature. The professor would later attempt (and fail) to steal the Philosopher's Stone, but even with Voldemort's strength aiding him, he was killed.