Ronald Weasley - Ron is the best friend of Harry Potter and Hermione Granger, and sometimes clashes with both to be launched in the background (by the fame of Harry and Hermione in the high notes).

Hermione Granger - Hermione is the best friend of Harry Potter and Ron Weasley, and stands out for its high intelligence. 

Albus Dumbledore - Dumbledore is the headmaster of Hogwarts. He is the founder of the Order of the Phoenix, a witch organization that aimed to fight Lord Voldemort and the Death Eaters. It is considered by all the most powerful wizard of his time, almost equating to Merlin (and despite the humility, Dumbledore admits to being endowed with a superior intellect to normal people). 

Rubeus Hagrid - Hagrid is the Keeper of the Keys and the Land of Hogwarts. In 1993 he was chosen as teacher of Care of Magical Creatures. 
Although it is very large in size, it seems that no one suspected the fact that he is half-giant because he always said that his size was to have been the victim of a magical accident. 

Severus Snape - Snape got the place of Potions teacher at Hogwarts, with the oath to protect Harry, but that was not exactly your desire because the chair he'd occupy was the Defense Against the Dark Arts, and Dumbledore surely would not allow a probable Death Eater that matter to teach school students, who were trained for more but in the sixth book he conseque the post of professor of Defense Against the Dark Arts. 

Draco Malfoy - He is the son of Narcissa Black and Lucius Malfoy, renowned (and rich) Thoroughbred time or another assists the Ministry of Magic with large sums of money, getting through it contacts and prestige in there is also a Death Eater Lucius Death, supports and agrees with the ideals of Lord Voldemort. 

Lord Voldemort - He is considered by many the most powerful dark wizard of all time, whose goals are to control the wizarding world, gain immortality through the practice of the Dark Arts and spread the superiority of purebloods before Mudbloods . He is so feared by the wizarding people who are referred to as ("You-Know-Who" or "You-Know-Who") and "He-Who-Must-Not-Be-Named" or "He Whose Name Must Not being Pronounced "instead of his own name. It is also called the "Dark Lord", but usually only by his followers, the Death Eaters (Eater) Death.