Base Breaker: The military adviser Julius Kingsley turns out to have been a Lelouch brainwashed by Emperor Charles to do his bidding before he sent back to Ashford Academy with Rolo. While some people were happy to see him even before his identity was confirmed, others were less happy about his significance in the story, having felt that he might have overshadowed the main cast a little too much.
Broken Base: Early into the OVA, the Code Geass fandom became divided over Akito for different reasons. Some preferred to see the original cast back instead of the new characters, while another faction was glad to see a different side of the fictional universe and quickly warmied up to the changes. Others didn't like how the overall tone of Akito is far darker than even the first season of Code Geass, which appeals to the tastes of certain viewers who thought the original show was too goofy, but not necessarily everyone else. On the other hand, the brief appearance of Suzaku and "Julius Kingsley"/Lelouch in the second chapter was also divisive, with some welcoming this turn of events because they missed seeing familiar faces or at least felt it would make the situation more interesting, while others feared the risks of reusing characters and concepts from the main series. As it turned out; Suzaku and Lelouch do get some decent screentime, but the main focus is still on the new cast.
The ending has also been rather divisive; besides the arguments about whether it was rushed and/or too happy, one of the biggest disputes revolves around the sudden increase in the inclusion of supernatural elements, and whether they fit the show or were simply hamfistedly shoehorned in.
The fandom has also become divided on Lelia's Geass ability; some feel it is overpowered and contradicts canon on how Geass powers work, while others believe that her power is perfectly consistent with what the main series has already shown, with the latter also liking that it actually fits her personality.
Crazy Awesome: The second episode has Akito channeling his craziness with his allies to increase their abilities. It's like if Sunrise took notes from this trope.
Darkness-Induced Audience Apathy: The show is very dark, to the point where the differences between the EU and Britannia seem almost minimal. Which, along with the other reasons mentioned in this page and the fact that the EU ends up being defeated in R2, may possibly make it hard to care too much about what happens in the series. That said, later episodes do bring back some of the idealism and even lightheartedness that were also present in the original show.
Esoteric Happy Ending: Depending on what you focus on, the ending can be seen as this. Akito's ending was, like Code Geass: R2's own ending, seen by some viewers as being rushed and too happy, though there were also others who felt that the "happy" aspects were undermined by the fact that Britannia ends up conquering Europe during R2. But it can also be said that the ending wasn't necessarily meant to be a truly "happy" one for the E.U. as a faction in the first place.
In fact, even the creators of Akito have commented on the difficulty of writing a side story when the fate of this fictional world couldn't be changed. From that point of view, the finale wasn't really meant to solve all of Europe's problems. It is just a way to give the main cast of characters closure and an opportunity to escape from the complications of politics and warfare after overcoming their own personal struggles.
Narm: The ridiculous amount of racism in the first episode: if there's a chance for a European character who's not Leila to be racist, they will usually try to take it. It's a bit overblown, at least compared to the original series.
For example, when Akito threatens a person by employing a racist claim about how good his people are with sharp objects, although it later turns out he was actually half-joking.
Reality Is Unrealistic: The treatment that the Japanese have is based on the real phenomenon of Displaced Persons or DPs. Some of the biggest waves occurred after World War 2 and cause considerable friction to this day, however to younger generations the phenomenon isn't as well known. That said, Akito the Exiled takes the concept and drums it Up to Eleven. Only in Code Geass is it politically correct to use DPs as kamikaze units (not to mention sacrificing high tech military equipment along with them), as well as go through the full Ghetto treatment even in the resident Federation. Thankfully latter episodes play this down considerably.
Additional Narm comes from the scene in episode one where Akito shows his military ID to that one truck driver. Previously, the truck driver had treated him like a fellow EU soldier, but afterwards he looked upon him in disgust. And that's before Fridge Logic sets in: shouldn't the truck driver have recognized Akito as Japanese up front by his facial features? Perhaps he initially thought Akito belonged to another Asian ethnic group instead, but this isn't made clear.
That said, the overblown racism seems to be deliberately invoked, as the European elite seem to encourage anti-Japanese discrimination at least partly to allow them to exploit an ever-replenishing supply of cannon-fodder, since they couldn't sell an otherwise stagnant and unpopular war to the general public.
Some of the angry Torches and Pitchforks rioters in the third episode look kind of funny. In addition, their apparent readiness to go that far so quickly is also somewhat amusing to see.
Akito's Geass makes him and anyone it spreads to scream "DIE" over and over.
Shin Hyuga Shing's Knightmare, Vercingetorix, is a mixed bag, if not for how extravagant it is. The axe is way too intricate (most of it being clock gears stacked on top of each other in a physically impossible manner) and yet it rips apart Akito's Alexander just fine. Additionally, he enters into the fight in its centaur mode, with the mech's golden plating making it all the more jarring. That said, the knightmare actually looks very intimidating, while the centaur mode is actually practical (considering its sheer mobility).Overall not something you'd want to run across in a battlefield.
Seeing Lelouch/Julius Kingsley putting a crazy plan into action again as a would-be Rabble Rouser who stirs up the European masses. The outcome might feel exaggerated in terms of more or less stretching the viewer's logic, but that over-the-top nature is one of the elements people enjoyed about Zero's plans, regardless of just how unrealistic several of them turned out to be.
Pandering to the Base: Some fans believe the appearance of Julius Kingsley Lelouch as the military adviser for Euro Britannia was thrown in as an attempt to attract Code Geass fans who wanted more of Lelouch. From that point of view, all of Julius's screentime and actions could have gone to Shin instead and the OVA would have been the same. However, the director of Akito the Exiled has gone on the record to state that he wasn't really thinking of pandering to the fans: according to him, the inclusion of Suzaku and Lelouch as guest characters playing a limited role was meant to depict them as symbols of the unchangeable world and their limited interactions served to portray his own interpretation of Suzaku's complicated emotions towards Lelouch at this point in the story.
They Wasted a Perfectly Good Character: Based on what some of Suzaku's fans expected, his appearance in Akito would qualify as this. They wanted a more detailed exploration of his actions between R1 and R2, showing all of the development from his R1 self to where he was by R2. Instead, they were disappointed by how he basically plays bodyguard to Julius/Lelouch and only gets one Knightmare fight and then spends the rest of his screentime being held as a prisoner with Lelouch. From a different point of view, Suzaku's character had already been explored during the TV series. Giving him a lot more screentime would have risked overshadowing the new cast of characters, so it would be difficult to achieve a balance that could please everyone. Even though Suzaku's development wasn't shown in detail, his few scenes still depict an interpretation of the internal tension between his feelings of hatred and friendship after the events of season one.
Andrea Farnese and, to a lesser extent, the other leaders of the Euro Britannian Knightly Orders count as well. The former, suspecting Shin of being responsible for his friend Manfredi's death, makes a declaration at the end of episode 3 that implies he might try to deal with him, and is later revealed to have been at Mandredi's side when he first met Shin. All of this ends up coming to nothing in the end, with Andrea only getting a small cameo at the end of episode 5. At least he's treated better than his two colleagues, who receive no focus or plot involvement and simply end up being killed by Shin off-screen.
The Asura Strike Force and the Knights of St. Michael's three Swordmasters could have made for interesting recurring Elite Mooks for the W-0 unit, with the same potential for character depth that Ashley and Jean got. With the exception of Ashley himself, the rest of the Asura Strike Force only gets one fight onscreen and are left out of the final battle, while the Swordmasters are only introduced in the last two episodes and get little screentime to truly showcase their abilities.
They Wasted a Perfectly Good Plot: While Akito the Exiled does give the European setting a lot more detail and attention than the original TV show ever did, the limited running time also means there was even more that could have been done. The European Union is noted to be plagued by problems with populism, bureaucracy, rising tensions and racism against refugees who are denied citizenship unless they choose to fight, and being at war for seven years by the time Akito starts. All of which could have potentially led to interesting developments for the characters and factions. After the first episode it's barely given any focus again outside of riots caused by Lelouch's over the top plan, which ostensibly acted as a trigger for the underlying tensions, and the very quick rise and fall of Smilas through his populist/dictatorial exploiting of Leila's attempt to the calm the masses.. Ultimately, the ending was concerned with the fate of the main cast of characters and not on addressing the social or political issues involved.
This also includes the refugee camps where Japanese people ended up in, as shown in episode one of Akito. Apart from a brief scene showing concerned Japanese during the riots in Paris, the ending makes no mention of what happened to the Japanese stuck in the camps or in service to the EU. Leading their fate to potential Fridge Horror or at least a desperate evacuation by the time Britannia conquers France in early R2.
Euro Britannia is noted at points to have concerns about how the homeland, and in particular Emperor Charles, acts towards the rest of the world. Unfortunately, due to how little we learn about Euro Britannia as a whole, with regards to both its characters and its ideologies, the faction as a whole ends up feeling rather underdeveloped and underutilized. There are other interesting details too, such as the more chivalrous nature of their military orders compared to regular Britannian forces, that were established but not necessarily fully explored.
Many people felt that Akito had way too much material for a short OVA, and that it would have been better off as a full-fledged multi-season show. Making the latter would have allowed for an expanded plot and increased character development at a more believable pace, and for the ending to not feel as rushed as some fans felt it ended up being. There is a novel adaptation of the story that apparently goes into more detail than the OVA series about several of these aspects, but it's still a shame that the animated version didn't.
Unintentionally Unsympathetic: The main characters (minus Leila) initially fall into some of this (and even Designated Hero) in the early episodes. The titular protagonist is Ax-Crazy in battle and kills enemy pilots quite ruthlessly, while the other three Japanese characters are criminals: one even blew up a building with students still inside, which despite his Freudian Excuse was a bit excessive. Overall, this might be considered the largely inevitable consequence of creating a Crapsack World setting, but it could also be hard to root for the good guys at times early on, especially when many of those running Euro Britannia are surprisingly honorable. That said, the main heroes all eventually mellow out considerably.