I mean, I wanted to avoid any in-depth discussion on specifics until I'm actually done with the game since the Reverie Corridor is still a thing but...
I'd say characters that I felt had weaker roles here were (in no particular order): Olivier, Agate, Wald, Millium, Elliot, Laura, and Musse but I don't particularly know if I like them less after all this (with the possible exception of Agate because I feel like Falcom keeps getting closer and closer to taking the plunge on the Tita ship and making him seem more okay with it and just.... no)... like it's not like any of those did something that tanked my opinion on them. They just either didn't do much or I didn't particularly care for the direction they went.
I consider this distinct from certain plotlines I did not like. I feel like I mentioned a few of these as I went but: I still think the plotline of Lloyd and the SSS "losing their way" was completely forced and not reflected in their actual attitude. It's just, I don't really count that against any of the individual characters too much because as forced as I felt it was they didn't really linger on the point much and beyond that it kind of ended up distributed over the entire SSS since they all just claim they felt the same rather than it all falling on Lloyd. The Ilya plotline also fell pretty flat for me and probably no surprise it is a pretty close parallel to the SSS one. Weirdly I think it reflects less poorly on *Ilya* because hell I'll take any angle on her character that isn't "commit crimes against Rixia" even if the actual *plotline* I disliked more because it was much more front and center.
---
May you find your book in this place. Formerly known as xp1337.