Naruto:
I hate how after the time-skip Naruto hadn't learned anything remotely useful except for the Oodama Rasengan (which was used what, once?). I hate how Kakashi seems to be getting weaker. I hate that Sakura stopped being useful after the Rescue Gaara Arc. I hate how new characters Sai and Yamato haven't gotten nearly enough attention as they deserve. I hate how the cool supporting cast, especially Rock Lee, seem to have been down-graded into background characters. And most of all, I hate how Sasuke made part 2 all about him. I actually like his character, but nobody but the main character deserves that much attention. I stopped reading after the Kage Summit Arc (so that I didn't spoil myself with the anime), so I don't know if any of my issues have been adressed. I have heard that with this new arc that the supporting cast is getting some attention (finally!).
Bleach:
The whole Arrancar Saga was pretty alright in terms of story (albeit way too simple compared to the awesome Soul Society Saga), but it definitely didn't have to last as long as it did. Kubo managed to get even slower in terms of pacing. Here we had a simple storyline that lasted more than 4 years! I started reading the manga again with this new arc, which is just so refreshing compared to the hideously long arrancar storyline. I hate how little attention the main group (Chad, Ishida, Rukia, and especially Renji) got compared to the captains. I have to agree with everyone who said that Kubo had literally no idea what he was doing with this saga. Hopefully this new arc will be much better planned and paced.
One Piece:
No complaints except for the slow, slow pacing. While nowhere near as slow as Bleach, One Piece manages to stall even with chapters that seem well paced. Did Skypeia (which is one of my favourite arcs by the way) have to be so long? And Thriller Bark also. I hope that one day there will be a "One Piece Kai" so that I can watch the whole series in a normal pace.
D.Gray-man:
Somewhere along the way it started to get a little boring and difficult to follow. I think it all started with the special chapter from Akamaru Jump. Suddenly we got a whole bunch of characters, who in my opinion should've shown up gradually, we got weird/ugly white (at least to me) uniforms for them, and the pacing just got reallly weird. The series being in Jump SQ is probably a good thing, but every chapter confuses the hell out of me. And although Katsura Hoshino's art is great, it seems to have worsened compared to the chapters just before the magazine change. The art itself contributes to the pacing/confusion issues.
Katekyoushi Hitman Reborn!:
The Future Saga was pretty good I think, but man did it have pacing issues. It started out alright, but during the Melone Base Arc, everything got much slower, and did Amano really have to pull out the new villains out of nowhere? I think they should've been properly introduced. Then we got the Choice Arc, which was shaping up to be a pretty exciting and strategy-filled wargame. But it only lasted one round! I wish it would've continued a few more rounds, the last round being the final battle of the saga, but no, it ended abruptly and what we got was a hideously fast-paced arc and final battle. Because of that, the new villains got zero character development, the fights were unexciting, and the everything just felt so rushed.
My other complaints include how the fights gradually lost their strategy element. The box weapons were pretty cool, but the box animals were a horrible idea. For a while it felt as though I was reading a Pokémon knockoff. And the characters just keep getting upgrade after upgrade, instead of developing different strategies. Oh, and Ryohei, Lambo and Chrome were largely ignored when it came to fights.
Even with these complaints, I still find myself enjoying these series

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