Abandon Shipping: The reveal that Ayame's Diver, Aya, is a high-schooler drove off a fair amount of Ayame/KO-1 shippers, given Nanami is out of school and Koichi is even older than she is making for a pretty significant age gap.
Ass Pull: The 00 Diver Ace's Energy Wings. While Super Attacks were mentioned earlier via Tigerwolf, Riku never bought one with his Diver Points like Tigerwolf suggested. It comes about when Sarah admits her feelings about being with everyone, so it comes off as an awkward moment of The Power of Friendship. Even worse, it comes at a point where Only the Author Can Save Them Now as Tsukasa's Break Decal power was so strong, not even Trans-Am could break it.
Was Do-ji determined to attack Riku just to get revenge for his loss, or that he wanted to prevent the latter from spilling the fact that he collects Diver Points from newcomers by baiting them? After all, his brother Ogre is a person who has distaste for those who cheated others.
Many Western Gundam fans were left scratching their heads in response to the news that the show got a second season. Values Dissonance plays a big part in this, as Build Divers relies on a lot of aspects of Japanese MMOs that don't apply to western ones (mainly concerning the perceived incompetence of the moderation team), leading to Western fans to interpret several instances of Reality Ensues as instances of Idiot Plot. It doesn't help that Gundam fans in the US are older than the intended audience of Gundam Build Divers.
Badass Decay: Many fans seem to believe that, because of some of force Build Divers' wins, this has been hit towards characters like Kyoya and Rommel. Episode 15 had these accusations raised highly as Avalon lost 5 times and the 7th Panzer Division lost 7 while Build Divers got it on the first go with a notable complaint being that, being Rank 1 and 2 respectively, they should have beaten it already.
There would have been more tension about the identity of the mastermind behind the Break Decals as Koichi's friend from GBD, Tsukasa Shiba if his appearance in the flashback from episode 6 didn't have him wear the exact same outfit he wears in GBN as opposed to his more casual clothes from his later in-person appearances.
Sarah being revealed as an AI is treated as a shocking revelation, but fans had called it as early as episode 1 due to fitting into common MMO cliches. Her mysterious powers and the fact that she is the only character who is acknowledged to lack a gunpla yet visit GBN anyway are also dead giveaways.
Due to a number of visual cues both in the opening and in the first episode, many fans were convinced that Nanami was actually Magee, pulling the Obfuscating Stupidity card to keep people from putting two and two together. This was pretty much jossed as of Episode 6 with scenes featuring both Nanami offline and Magee online at the same time, and ultimately debunked as Nanami later joined the game with her own distinct avatar.
Fans deduced pretty quickly that Tsukasa was out to destroy GBN as revenge for it indirectly depopularizing Gunpla Duel and hoped to bring back the old way of Gunpla battles. This was confirmed in episode 12.
Seeing how incompetent the administration of GBN has been about the Break Decals, some fans have postulated that some, part or even all of the administration is working with Tsukasa in some capacity. Turns out they really are just that incompetent. None of them are working with Tsukasa.
The Gundam 00 Diver's is actually an Incredibly Lame Pun in Japan. The suit's name is read "Double-Oh Diver" in both English and Japanese. However, the Japanese, because of phonetics, would pronounce it as "double oh daiba"... or more easily "double odaiba". Odaiba is where The Gundam Base is located in Real Life. Not as bad as the A-Z Gundam in Gundam Build Fighters Battleouge being a one big Amazon.com reference, though.
Tigerwolf and Shahryar can pull off a Combination Attack of sorts called "Soukyoku Silk Road". The Silk Road is the legendary trade route that cuts across Asia, connecting China and the Middle East, which is precisely where Tigerwolf and Shahryar are themed after, acknowledging how they're Not So Different.
An important scene in Mobile Suit Gundam: Iron-Blooded Orphans has Cookie and Cracker Griffon very nearly get hit by a car, but found lying on the road anyway. Here, Do-ji, who resembles their brother Biscuit, is apparently guilty of pulling a Flopsy.
Episode 6 has something of an Enforced Plug, with Koichi shown with the newly-released MG Deep Striker in a flashback. Apparently the backlash over the actual Deep Striker model is what broke up Koichi's team.
The fan backlash against Build Divers' departure from Build Fighters' setup became this as it turns out that GBN's low-risk gameplay practically replacing classic Gunpla Battles and their heavy risk lead to the villain having the exact same reaction as those fans.
Ogre's Hannibal Lecture to Riku in episode 21 is mostly him accusing the latter of relying solely on Sarah (i.e. a bottomless supply of Deus ex Machinas) to reach the top tiers at such a rapid pace - something that the series up to that point was constantly criticized for.
Just Here for Godzilla: As the series continued, many fans began stating they were only watching the series for Ayame, the obligatory Patrick Colasour cameo for the episode, and any sighting of Magee's tightly sculpted ass.
"This week on the Colasour Chronicles..."note A play on the Meatbun Chronicles meme from Gundam Build Fighters, where viewers will immediately hunt down the recurring Patrick Colasour cameo in every episode.
On a related note: "This week on the 'DAT ASSE' Chronicles..."note Much like the above mentioned example, but this time focusing on Magee and his very pronounced posterior. The misspelling was apparently intentional in this case.
Many fans have begun referring to Koichi and Ayame as Shiroe and Akatsuki due to their striking resemblance to each other.
When your mom says "Take your brother with you"note In episode 9, we see that Do-ji is teased and mocked by the rest of Hyakki because of his lack of skills compared to Ogre. Along with Do-ji's "skill" in episode 1 and his sputtering acts in later episodes, it makes Do-ji out as a Memetic Loser
Oh, hey. Big Zam.note A meme that originated from the Game Grumps, which made a minor resurgence after an oversized Big Zam appeared as the final boss of episode 12.
"My life forAya!"Note Upon the introduction of Aya Fujisawa (aka Ayame, outside of the GBN), some diehard fans of hers have taken to adopting the well-known Protoss battlecry as their form of adoration.
DAN KUROTO LIVES!Note In Episode 18, one of the Divers listed in the Ranking Boards is named "Genm". People instantly made the connection to the infamous Large Ham.
Misaimed Fandom: Big Bad Tsukasa Shiba suffers from this. He's played up as a Stop Having Fun Guy who hates GBN because it's not his type of gameplay style and that those who enjoy it are nothing more than fakers who will never understand a real battle. While we are meant to side with Riku and that both kinds of gameplay are both fun and we shouldn't dismiss the other for being different, some viewers, especially those who hate the series, side with Tsukasa because his actions are trying to bring back the Gundam Build Fighters-style of fighting.
More than probably any other mainline Gundam series, Divers is aimed squarely at a younger crowd. Yet while it's underperforming in its target demographic, it is relatively overperforming among teens and young adults. The number of Mythology Gags might keep older Gundam fans coming back even if the show might be a bit simplistic for them.
There is also a not-inconsiderable number of furries who are there solely for Rommel, Tigerwolf, and Shahryar rather than the plot or the Gunpla. The presence of many background characters with similar traits has only boosted the appeal, especially with regards to self-insertion work.
Thanks to the extremely genuine portrayal of Magee and the not particularly subtle Foe Yay going on between Tigerwolf and Shahryar, there is also a noticeable niche of LGBT fans.
Ron the Death Eater: As far as some viewers are concerned, Team Build Divers consists of a bunch of cheaters who leech off of Sarah's powers instead of winning through legitimate means. Note that they were completely unaware of the truth about Sarah until the final few episodes, and how Sarah is only explicitly shown to help with two of their victories (to stop the Story-Breaker Power of Tsukasa's Big Zam and to destroy a rock that was about to crush the members of the Nadeshiko-lathon, the latter of which was caused by Sarah's presence causing glitches in the first place).
Rooting for the Empire: An unfortunate side-effect of making Tsukasa's motivation be tied so heavily into the Build Fighters style of fighting is that some fans who also disliked the change found it easy to sympathize with him.
So Okay, It's Average: If you're willing to look past the ways the show differs from Build Fighters, the series is rather simplistic and meant more for kids than anyone else.
In episode 4, when Nanami shows off the rental Gunpla, it is quite obvious that all except Airmaster, Aile Strike Rouge and Ball are just clip art of various mobile suits. As well, Harry Ord's Gold SUMO turns into a normal SUMO the very next scene.
When Ayame is warming up for the Nadeshiko-athon, the show represents her jumping by literally moving her static character model up and down. Thankfully she's not the focus of the scene but it's a jarring bit of Limited Animation.
Slow-Paced Beginning: Viewers were wary of the series due to the fact that it started off very slowly by spending its time with massive world-building and its slower-paced fights. They started to come around starting with episode 10, citing the rising stakes the apparent conclusion to the Break Decal storyline was bringing about as well as diving into Ayame's backstory.
Superlative Dubbing: Upon hearing the dub, even many fans who disliked the series were actually quite surprised at how well it was done. One of the many positives people have noted was that Riku, Yukio and Momoka's voices are just a little more older-sounding, thus they don't come off sounding like a bunch of little kids.
In a similar vein as Mobile Fighter G Gundam, Gundam Build Divers is an alternate universe take on Gundam Build Fighters, hiding a dark plot to ravage a video game world out of sheer jealousy within your standard shonen-type isekai-like series, toning down the insane, high-octane fights for something a little more standard and grounded and focusing on world-building and character development. To that end, fans who loved Gundam Build Fighters and Gundam Build Fighters Try dislike Gundam Build Divers for those changes, claiming its too much for kids and there's nothing at stake.
The High Grade Galbaldy Rebake kit had upset half of the fans for not resembling the stylized look present in the show (the show design cheats to turn many of the rounded parts of the original Galbaldy into hard edges to better resemble Mobile Suit Gundam: Iron-Blooded Orphans designs).
The Astray No-Name High Grade kit got criticism for not being color-accurate to its anime depiction (its only appearance at the time of the kit's release had it fight in a battlefield with brown light that made its black parts look brown, but the stock photos and all other lineart of it keep the sections black) and the articulation of the new parts being somehow worse than the 2013 kit it's based off on.
They Wasted a Perfectly Good Character: To be fair, a good number of characters present on the show such as Koichi, Momoka, Yukio, and Ayame aren't bad (nor even horrible) at all; The main problem with them is that they tend to be overshadowed in importance by Riku and Sarah, who are serious Base Breaking Characters that are said by many Gundam fans to be the biggest factors that really bring the show down!
One particular Reddit user had this to say in regards to this:
Episode 6 featured the old style of Gunpla Battle, harking back to the style of Gundam Build Fighters and Gundam Build Fighters Try. Except we only get to see one full fight with this style, which many fans expressed disappointment for because they found said fight to be a highlight of the show.
The second opening and ending suggested that Nanami would become a Sixth Ranger, but this is rather quickly dropped, despite the end of her first episode in GBN hinting that she would build a gunpla of her own.
An unfortunately large number of gunpla from the second half of the show don't get much screentime and serve minor roles at best. Special note goes to the GBN-Base Gundam, which as the powered-up version of the GBN-Guard Frame that was involved in a plot-heavy moment, would be expected to serve a major role. Instead, it appears for less than a minute in the final episode as a One-Scene Wonder.
The dark version of Sarah is initially implied to hold quite a bit of plot significance with the way she is foreshadowed. She is however never fully used and only really appears in a single scene before disappearing from the plot.
Tough Act to Follow: Gundam Build Divers follows in the footsteps of the near-universally well-received Gundam Build Fighters and its more divisive, but still ultimately considered decent, sequel, Gundam Build Fighters Try. However, where this series lies in people's eyes tend to be a hotly contested subject as there are some who feel that Divers just can't reach the original Fighters but surpasses Fighters Try while others believe that Divers is worse than Fighters Try.
They only show up as a short Cameo in episode one, but really, who expected the prehistoric mobile suit blobs from the Mobile Suit SD Gundam Mk V short "Genesis: Pikilienta Pohles" to make an appearance? Riku and Yukki certainly look surprised to see them.
Several gunpla from the show's side materials show up in the final episode, to the shock (and joy) of many viewers.
Unintentionally Sympathetic: Game Master and the admins who want to delete Sarah are clearly shown to be in the wrong. As much as GBN is Serious Business, the narrative and viewpoint characters see Sarah as a person, albeit a digital one. However, due Riku's immaturity along with the logical fact that GBN being destroyed would result in Sarah's death anyway, plenty of fans see the decision to patch Sarah as being a pragmatic Shoot the Dog rather than being a potential Moral Event Horizon.
The Un-Twist: Episode 20 has the shocking reveal that Sarah, the Mysterious Waif who is only shown in the game and has special powers, isn't a human at all, but actually just a digital entity that exists only in GBN. This was so blatant from the first episode that the only people surprised are those who thought the show couldn't take such a cliche path.
Values Dissonance: A major problem with Western fans concerning the GBN, which they claim breaks the Willing Suspension of Disbelief, is that the Mass-Divers seem to wreck havoc with impunity, allow the Break Decals to try to damage the game itself, and that the Divers themselves are the only ones to stop them with no GM, Mods or Devs around to slap the banhammer on people. In Japan, many MMOs are essentially self-policed by the players and they rarely get GMs or Mods involved unless it is really devastating, unlike Western MMOs, where players will willingly hunt down GMs for even the smallest infraction. Indeed, another Sunrise and Bandai production, .hack, had the same concept, essentially allowing the fate of The World being rested on the players themselves than using the higher ups.
One that's mired in Truth in Television, but still this trope as Riku easily falls for Douji's Flopsy ploy despite the obvious acting nature and Yukio smelling a fish. He doesn't even realize he's doing something wrong at all.
A massive one in the backstory of Force le Chat Noir. Kozy could have gotten the newbies complaining about the use of SD Gundams to put their money where their mouth is by letting them use Real Type models while the founding members kept with their SD Gundams, instead of sacrificing any of the SD Gundams they had. Real type HG models are NOT that hard to come by.
The Woobie: Sarah. She's an AI in the form of an adorable young teenage girl that knows what she is, but feared of being seen as weird. Now she's being told that her existence is threatening the game and trying to fix this may kill her, especially now that she's being hunted by Game Master and the administration for existing.