OMFG
I kinda always thought assassin classroom as half goofy series with some short of seriousness in season 1.
I kinda treat is as above average-ish, rather than "good" because of the Koro-sensei non-serious attitude / goofy design
But season 2 was much different.
1st half of it was kinda continuous goofy-ness with slice of life / character background storyline.
2nd half made me in soooo much emotional rollercoaster that caught me by surprise
It wrapped nicely with manga ending, really recommended to watch both season immediately.
KORO-SENSEI!!!!!!!
Oh, I also finished Wixoss season 2 which also wrapped the story neatly.
Without spoilering it much, think the series as Madoka Magica + Yugioh