Even though I was a huge fan of Reborn, I agree with hatsuharupeace by saying that its ending was disappointing.
Can't forget Psyren either. It was a great manga, I enjoyed reading it, but it ended too quickly and without a satisfying conclusion. Sad it got canceled because it had tons of potential.
Also makes me miss koen's announcement of next chapter being out. :'(
Honestly though, i felt that the end of Psyren was satisfying considering that it was cancelled
I have to say out of all the manga I have read and that have finished, Air Gear was a mess. By the end of it, I really didn't know what was going on and it definitely felt like a rush. I kind of got the feeling that Oh Great! really didn't want to draw Air Gear anymore.
Hitman Reborn, end of story...alright fine I'll elaborate a bit
I was really disinterested with the series once it got into the future arc; it was long, boring, unnesesarily dark and the power system was hoping around like a rabbit on crack until it finally fell of a bridge and drowned. I still stuck with the series because I was in that naive mindset when I was waiting for Bleach's boring arc to be over with "its just one arc, it can always get better later~!" It didn't for me honestly and so I dropped it but picked it up again to see the last few chapters since I heard it was ending. Now I honestly didn't care much for the final confrontation with checkerface or whoever the hell that guy was but basiclly it ended on "Oh, I'm still a pathetic dipshit who can't do anything on his own, but hey, at least I have FRIENDS~"
I facepalmed and Groaned.
Now in certian series I don't think this sort of thing would be all that bad, but what irritates me is that the whole issue with Tsuna being the boss is once again sidestepped and even though he has friends, he still seems so pathetic he still has to rely on either them or his super pills (the original power pill popper before hodi!) The fact that he isn't ready to not only take on the responsibility nor try to avert his fate, which is something I was acctually hoping he'd try in the begining, is just frustrating when you consider we've been follwing this guy for over 400 chapters, the fact that nothing gets resolved like this is just utterly ridiculous to me and only made me wonder why the hell I even bothered with the series to begin with.
goodness, I might be the only person who *liked* KHR's ending.
Worst ending? Phuu... It's Shaman King, innit. We had years of having that horrible non-ending, and the slow decay of the series that led to it was just crappy enough to make it all the worse.
Since no one mentioned it, Mx0 being cancelled and thus ending terribly was tragic. The Japanese have no taste.
Bakuman's end was less than amazing, but when a huge fan like myself had to stop reading the series on a weekly basis until it ended because the series was getting ridiculous, that is to be expected.
FMA's ending was pretty much terrible, but I was never gaga over the series.
Yu Yu Hakusho's ending was weak, but the series was actually pretty terrible as a manga. (The pacing was terrible. Everything happened at warp speed. How weird is it that I consider the anime dragging things out a good thing?)
I can't recall any shojo or romance series that I thought had a good ending. (They usually have some idiotic final event or just drift off)
Since Cage of Eden appears to be ending in 3 chapters (my bet is it is being cancelled), I'm going to preemptively put it on this list. It looks like it is going to do a hatchet job to the mystery of the series then have nothing be resolved.
And on that note, I'm fairly certain that 3 once popular series that are on their last legs will make these kinds of lists when they end if for no other reason than their massive decline. (Bleach, Gantz, and Naruto)