Defense against the dark arts

After Dumbledore's refusal to give Tom Riddle the defense against the dark arts job, no teacher has been able to hold the job for longer than one year.

Year 1: Voldemort himself (not a vary good teacher, as he is the worlds most famous dark magician)

Year 2: An impostor (only good at memory charms, until one backfires from a broken wand)

Year 3: A werewolf (very inconvenient on full moons)

Year 4: A death eater (better than Voldemort, worse than a werewolf)

Year 5: A ministry devil (worst detentions ever)

Year 6: A person who hates him (he needs no introduction, Severus Snape!!!)

In the 5th book, Hermione persuades Harry to lead a defense against the dark arts club under professor Umbridge's nose. The first few meets are legal, but with Educational Decree 24 soon active, they continue to meet in secret in the room of requirement.