Harry Potter: Ranking All Defence Against The Dark Arts Teachers From Worst To Best
3. Barty Crouch Jr. (as Mad Eye Moody)
While Mad-Eye Moody is never technically one of Harry’s Defence Against the Dark Arts teachers, Barty Crouch Jr’s impersonation of the former auror is so spot on and dedicated that he may as well have been, thanks in no small part to a lot of help from a well brewed polyjuice potion.
Passionate about the subject, perhaps due to the fact he is Lord Voldemort's inside man, Moody/Crouch is the polar opposite to Dolores Umbridge, taking the stance that you can never be too vigilant. His unforgivable curses lesson was perhaps a bit intense, not to mention illegal, yet at least he was trying to teach the kids something they could actually use.
By showing his students the unforgivable curses in person, he is able to demonstrate why they are named as such, even going as far as to mentally scar Neville Longbottom in the process. This lesson, as well as turning Draco Malfoy into a rodent, shows both his competency in the subject, and his ruthlessness as a wizard in general.
On top of his practical and knowledgeable lessons, he also successfully guided Harry through the potentiall fatal Triwizard Tournament, though his methods were questionable and his number one priority was always with the Dark Lord.