Recently read Bleach out of boredom and having generally ran out of series to watch/read. Albeit unbelievably generic and schematic to the extent it seemed like a parody, it was pretty entertaining and there were a couple of cool characters (Kurotsuchi Mayuri fuck yes), and so I guess listing bad chars is somewhat worth it.
First off, Ichigo. He's actually somewhat funny and all, I like him when they're messing around in the "mortal world", but I seriously dislike his fights. There just should be some kind of a limit to getting your body torn up and it not reducing your fighting ability in the slightest. And to completely random power ups out of the blue. I AM NOW TEN TIMES STRONGER FOR NO REASON THAN I WAS WHEN YOU BEAT THE HELL OUT OF ME TWO HOURS AGO.
The old man Genryuusai or w/e his name is. I was expecting him to be like really bad ass but it turned out he was just worthless, annoying and basically has done nothing up till the latest chapter.
I also totally hated Tousen, Byakuya, Renji, the weird animal-faced captain, Hitsugay and Yoruichi from the Soul Society arc early on, but Byakuya, Renji and Hitsugaya turned out to be somewhat better characters later. Tousen, Yoruichi and the captain guy are still lame and worthless though. Aizen and Gin are of course pretty annoying too.
I also generally hate arrogant and loud female characters, so the one-armed woman from the SS arc hella pissed me off. And his brother too.
The "vizards." Just no.
And the arrancar people. The ones who actually matter, like Grimmjow, Nnoitra and Ulquioirra are pretty decent but most of them just plain need to die.
Probably forgot someone.
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Guts from Berserk.
edit: Oh, I thought this was some old thread I'd already replied before. In that case I'll list some people from other series too from memory. I hope there's no char limit or something here. :[
OP: Coby (the young one), Morgan, Gin, Pearl, miss Goldenweek, mr. 5 (I think it's 5, the bomb guy nevertheless) and miss Valentine (basically I hated her laugh hella lot in the anime version and this hate carried on the manga for no reason [watched some of the anime version before starting to read the manga]), Vivi, Vivi, Vivi, Satori, Conis, Laki (w/e), Aisa, Franky Family, Paulie, Califa, Hogback.
Naruto: I read this one lately too for similar reasons as Bleach. Basically Shikamaru and Gaara were ok characters and, no exaggerating, the rest more or less annoying. Then post-time skip Shikamaru turned out pretty annoying too and Gaara a pussy, thus severing the last bonds to any hope the series could ever have had. Not resuming reading unless there's at least 100 chapters again to read at once when I happen to be in a situation with absolutely nothing else to do.
Ippo: Itagaki/Miyata, no elaborating needed.
Death Note: Near/Mello/Misaargh for again obvious reasons.
Akagi: The wimp Akagi fanboy, I can't recall his name or anything.
Yakitate Japan: FUCKING YUKINO JUST FUCKING KILL YOUR FUCKING SELF.
FMP: the twins from TSR, Gauron (actually a good character but he hella pissed me off, though that's obviously intentional).
Hikaru no go: the Korean team, mainly the Hon Suyitynuiyunuyuotypohtpjophong guy who even had a backstory, as though anyone would give a shit.
GTO: Miyabi was just plain annoying.
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Can't think of more atm.
Besides Naruto and Berserk, not listing shit series I hate such ass Haruhi, Lucky Star, Love Hina or FMA and crap like that with basically only bad characters, as the list would grow way too long.