I have the same criticisms for this season as I did for the one previous (ie. Korosensei being the only real enjoyable character, juvenile humor, & the student's lack of concern for how the fate of the world is in their hands for the majority of the season). Unfortunately, those are not my biggest gripes with this season.
The second season of Assassination Classroom starts with more of the same of what we have grown to expect from the series. However, about a third of the way in, the show takes a more "serious" tone, but does not handle it well. Minus the end villain, most of the new villains/obstacles that the main characters face never seem to take more than 2 episodes to overcome, and all it takes is for Korosensei or a student to do some talking to resolve the issue. Not that I expect everything in this series to be realistic, but the ease of overcoming obstacles by merely having a conversation really hindered my enjoyment of this season.
On a more positive note, I did enjoy finally getting to see Korosensei's back story & found the ending quite touching.
