I have a lot, honestly.
Tokyo Ghoul Re comes to mind. It really doesn't live up to the original series at all, tbh. I find myself not as immersed by the series as I was the original. It doesn't help how rushed beyond belief the anime version is, too, it's just not worth it.
Also... Black Butler, for MANY reasons. The anime only season 2 was okay, but the first season of the anime was far superior. Luckily, for the third season of Black Butler, it seems this season was erased entirely from the continuity, so... There's nothing wrong with anime original seasons or anything, I just felt this second season was never really want we needed for Black Butler.
Dog Days's second season also wasn't really something I cared for. I never really enjoyed the second season, it really just didn't grab me like season one did. :x Meh. Season three was much more fun, so I guess it's just the second season was just bad.
Aaand, the last one that comes to mind is definitely is FLCL, like the sequels are okay... but nothing beats the zany original OVAs, tbh.