1. Professor Quirinus Quirrell (Harry Potter and the Sorcerer's Stone): He's possessed by Lord Voldemort.
2. Professor Gilderoy Lockhart (Harry Potter and the Chamber of Secrets): A self-proclaimed expert who actually has little talent.
3. Professor Remus Lupin (Harry Potter and the Prisoner of Azkaban): A werewolf and a skilled teacher, much loved by the students.
4. Professor Alastor "Mad-Eye" Moody (Harry Potter and the Goblet of Fire): A very skilled Auror, who was unfortunately impersonated by Barty Crouch Jr.
5. Professor Dolores Umbridge (Harry Potter and the Order of the Phoenix): A cruel and authoritarian Ministry of Magic official who disallows any actual Defense Against the Dark Arts instruction.
6. Professor Severus Snape (Harry Potter and the Half-Blood Prince): Although he primarily teaches Potions, he takes over the Defence Against the Dark Arts class in this book.
7. Professor Amycus Carrow (Harry Potter and the Deathly Hallows): A Death Eater who takes over the class in the seventh book, alongside his sister.
Let me know if you have any other Harry Potter questions!