In the "Harry Potter" series, there was a new Defense Against the Dark Arts teacher every year due to a jinx on the position. Each teacher was different in their own way, and not always in a good way either! Some of them taught well and deserved their jobs, and others deserved to be fired at the end of the year.
But who's the best? Who's the worst? Who's in between? For purposes of this list, I took their teaching skills AND their personality into account because I personally believe that both matter in fact and in fiction.
1. Remus Lupin
Remus Lupin was by far the best DADA teacher to exist during Harry's school years. A kind man and an interesting teacher, Lupin deserved to stay in the position forever. He loved his students and his job, and he knew how to teach things that were appropriate for the third-years.
He challenged them without intimidating them or overworking them; he was gentle on them without babying them or boring them. He made sure that his students were aware of their full potential, and he always checked in to see that they were okay emotionally.
All of this makes his resignation even sadder; a great person/professor was forced to leave due to discrimination for something he cannot control.
2. Severus Snape
Say what you will about Snape, but you have to admit he wasn't a bad DADA teacher, especially when compared to some of the others. To be fair, "actually teaching the students and not lying about who you and/or not torturing students" is not a very high bar, but still.
When Snape taught DADA, he did the job properly - albeit perhaps a bit unfairly - and he was dedicated. He acted as a spy for the Order, so he does deserve some extra points for that. He may not be fully lovable as a teacher or a person, but as a character, he is interesting and complex.
3. Gilderoy Lockhart
Okay, he was not a Death Eater like some DADA professors were, so we have to give him that. Again, not a very high bar. Lockhart was an obnoxious man with an inflated ego. He made his class take a test on him rather than Defense Against the Dark Arts itself, for crying out loud!
Not only that, but he didn't even do any of the stuff he claimed, but rather stole the works of others before obliviating them. He gets a taste of his own medicine at the end of "Chamber of Secrets", and although you can't really pity him, you have to admit his fate kind of sucked.
4. Quirinus Quirrell
To quote Harry himself, "Yeah, Quirrell was a great teacher. There was just that minor drawback of him having Lord Voldemort sticking out of the back of his head!" Quirrell acts the part of a terrified and cowardly man, yet a decent professor.
However, he has a Dark - literally - secret. He supports Lord Voldemort, and even goes as far as to act as a host for him. He tries to harm and even kill Harry, right up until Harry does those things to him!
5. Mad-Eye Moody (really, it was Barty Crouch Jr.)
The real Moody would be tied for first place with Lupin, but unfortunately, we never got to see the real Moody in action. Crouch kidnapped him and disguised himself as Moody through the use of the Polyjuice Potion.
In addition, he forced Harry into the Triwizard Tournament, attempting to ensure the boy's death. As a teacher, he made his students see the Unforgivable Curses and even practice them on one another!
6. Amycus Carrow
Technically speaking, Amycus Carrow was just a Dark Arts prof because he taught zero defense against anything of the sort. He was a Death Eater and showed prejudice against pretty much everyone except pure-blooded Death Eaters.
He even made his students perform the Cruciatus Curse on people in detention!
7. Dolores Umbridge
Everyone hates Umbridge. She is mean, rude, and nasty. She hates Muggleborns and half-breeds, and she refuses to believe the very traumatized Harry about the death of Cedric Diggory and the return of He-Who-Must-Not-Be-Named. On top of that, she doesn't even teach her students any spells!
Umbridge also uses her power to establish nonsense rules at Hogwarts, trying to turn the school into a near-dictatorship. She is also fond of cruel and unusual punishment, just like Carrow. She forces Harry to carve the words "I must not tell lies" into his hand using his own blood!