I accidentally spoiled myself that Junko was the mastermind, but thankfully, not how or why she was the mastermind, which are really the more important and shocking spoilers, so the impact of the reveal wasn't dulled in the slightest.
I'm always happy when there's a female villain who a) isn't the right-hand man of the villain b) doesn't have sexuality as her core characteristic (while Junko is clearly turned on by the idea of despair, the fact of the matter remains that it's not her main motivation or defining characteristic and, more importantly, she never uses her looks or seduction to commit acts of evil) and c) is the main goddamn villain, so I appreciated Junko on the level that she filled all of those criteria, with a memorable personality to top it off.
That said, I'm unsure how much I liked Junko as a villain, and I think this might be because she was exposed as such so late in the game. She couldn't have been introduced any other way, I know, but I think in order for a villain to really resonate as villain to me, I need to see them being the villain, committing the atrocious acts, having presence on-screen, and not hiding behind a different persona. I did enjoy her time on screen, however, and the way she gleefully committed suicide, with the final shot of her rocking in a chair with Monobear in her lap, waiting to be crushed, was pretty chilling.
The reveal that she did it all because she had a hard-on for despair was another thing that left me with mixed feelings, partly because of all the build up, and partly because it had already been hammered in our heads throughout the games that Monobear wants nothing less than despair. It's tough, because I'm not sure what I'd have preferred out of it (and no, a tragic backstory is not one of them) or if I'd even change anything at all. It fits perfectly thematically, yet it left me feeling hollow. Maybe it's just a matter of taste, where I can't explain or convey it, it simply is.
I think I had a feeling the outside world was in complete chaos a while back, but the end of the world is always a fright-button for me, so the predicament the students landed in (to live in a building for the rest of their lives while hell on earth was happening outside; then losing their memory and finding out they've woken up two years into the future) was pretty goddamn scary. I thought the Monobear imagery was a little silly, though I like to think Junko had just tampered with and exaggerated some of the photos to induce more shock in the students.
I did like the very end, with all of them sort of reluctant at first to enter into a world that might or might not be in complete wreckage at this point, but ending in them having a unified sense of hopefulness that they'll make it through no matter how ugly it is.
Next up: my thoughts on the series overall.