So, I got season 3 (Used) on DVD and marathoned the whole thing (Being sick for the last week has really screwed up my sleep schedule.) and I really thought about why Aizen is such an annoying villain. I think it breaks down into three major things, two are on his head, one is on the head of the SS and pretty much everyone else.. (And beforehand, I don't have any reference shots from the manga, sorry. So, I will try to break the wall of text up a bit.)
First off, from everything up to the latest chapters, Aizen is the ultimate Marty Stu. I mean, he's more powerful than any of the other reaper captains, except Yamamoto, and that's before he got his hands on the magic 8 ball of death. So, why not just take over? I mean, if his "perfect hypnosis" bit works on someone forever, why not just flash everyone in the SS, everyone in the Rukon districts, then travel to the WotL and flash everyone there, and finally flash all of HM? And repeat every few years to get the souls that were in transition to reincarnation until he had everyone? Then, he'd rule all of the worlds without a problem. Even if that way was impractical, he could have taken over the SS a long time ago without a problem. Also, he always has an answer for everything. I mean, sure, most major villains do that, but he even has answers for things that haven't happened yet. Things that are completely ruled by chaos, he somehow knows will happen exactly that way. In the beginning, being able to trick the higher-ups, along with his peers, made a kind of sense. Hell, if I were the villain, I'd act all nicey-nice with the people I was about to screw over. Even convert a few subordinates. But there's still a point where someone's going to start poking around.
Secondly, all of Aizen's "Experimenting" with different Hollows and the hogokyu really should have been noticed at some point. Unless, of course, he's smarter than Kisuke and everyone else in the various R&D branches that have appeared over time. Although, that ties back into the first point, we'll come back to that later. I mean, if one of my teammates wandered off on some "mission" and then a weird kind of Hollow appeared, I'd kind of be wondering what the hell happened. Even though his "perfect hypnosis" combined with someone wandering around covered in an illusion of him would kind of cover it, eventually that guy would make a mistake. I mean, no mimic is perfect. Plus, wouldn't the guy feel different? Maybe that's why certain folks were eliminated before the story starts. Still leaves several plot holes.
Third, I really have to hand the SS a slap on the head. I mean, this guy has been running a scam for several hundred years and nobody noticed? Nobody at all? I'm sure someone like Kisuke or Unahona should have seen something before the whole first arc. I mean, logic dictates that these folks figured things out. And yes, I know Aizen pushed his hand with the Vizored at least with Kisuke. But come on. Were the Central 46 and Yamamoto that stupid that they at least didn't try to investigate? How many criminals have been convicted despite having "several witnesses" place them somewhere else? Yes, a bit rare, but still happens enough. One would think that a group of super-powered Hollow killers would have some kind of investigative skills. And even at the end of the SS arc, everyone just stands there and buy's Aizen's story hook, line and sinker. I mean, come on. The man just revealed he spent his entire time lying his ass off to you, but he's going to tell the truth on this one, right? And why didn't they just chop off his head? When Yourichi and Soi Fon had him pinned, a quick snap would have made the HM arc go away. Aizen's head would have bounced down Sokokyu Hill, the party would have cheered, and that would be it. Tosen and Gin would be stripped and beaten to death with ravenous badgers, and we could have all gone home happy. Until the next bad guy comes in, using the resulting chaos from Aizen's plot to cause more havoc.
From there, Aizen has sunk into the worst of villain cliches. He's gained so many, "Screw you, I'm all powerful and ruling your mind," moments that he's really gone off the track of what could have been a cool bad guy. I mean, he could have easily been one of the coolest villains ever. Even if there was a counter found to the "perfect hypnosis" ability, it would still screw with you. But now, we've got some hydra-Hollow-butterfly form now. (I swear, he's transformed more times that Sixshot...) Honestly, if Aizen pulls out of the ass-beating Ichigo is giving him with some lame-ass crap about knowing it was coming, I am going to be really pissed. Or, if the magic 8 ball of death somehow sucks up the attack, forms the Royal Key, and Aizen becomes the next emperor....
...Unless, all of this is Aizen's simulation of how things will turn out, and we're still in the SS arc. Then, when he makes his attempt to snag the hogokyu again, he gets his ass stomped into the dirt by Ichigo. That would actually be a pretty cool twist. And it would be all right with me.