Even though this is one of the critic's least favorites, a lot of people enjoyed it because Bellatrix Lestrange escaped from Azkaban.
Also, this is when Dolores Umbridge first appears, She starts as a simple Senior Undersecretary to the Minister for Magic, then she is the headmistress of Hogwarts.
This is also the movie when Sirius Black died. The beloved character sadly got murdered by Bellatrix in the Battle of the Department of Mysteries.
Overall, this movie was decent, but Dolores frustrated me.