* AlternateCharacterInterpretation: Some fans assume that Ben's return to immaturity might be caused by him accentuating his JerkassFacade as a way to prevent himself from getting too serious and as such prevent him from going KnightTemplar like he almost did at the end of ''Ultimate Alien''.
** Others seem to believe he has MPD. See the WMG page.
** Due to Dimension 23 Tetrax being introduced [[KickTheDog doing actual rampages in a human city]], a lot of fans assume [[spoiler: he is still evil, or at least less moral than his mainstream counterpart, and [[PsychoForHire just happened to have been hired by Azmuth at this point]]. This theory is further supported by the fact mainstream Azmuth has been shown hiring villains before (he did recruit Sunder in ''Ultimate Alien'' to get the Unitrix back). Also lending credence to this theory is that [[BountyHunter Sevenseven]] is also on 23!Azmuth's payroll, and does similar actions.]]
* AntiClimaxBoss: Dr Psychobos. The series builds him up as an EvilCounterpart to Azmuth and hinted he was more powerful than he appeared by having him easily subduing both his associates at one point. Moreover, he was one of the few villains to actually escape a confrontation with Ben while getting what he wants. Yet, he is easily outsmarted by Azmuth in "Showdown Part 1" without even displaying any fighting skills. Justified somewhat, after all Dr. Psychobos is scientist, not a badass fighter like Khyber and Malware. He wouldn't stand a chance in a straightforward fight against Ben and Rook and gets his ass kicked by Khyber with little effort.
** Sixsix, Sevenseven and Eighteight in ''Vilgax Must Croak''. For the whole episode, they pursue the Plumbers inside Incarceon and almost eliminate them, with a single one of them sending them running. When the Plumbers come back and confront them again... they immediatly surrender, despite being clearly stronger than them.
* AssPull: While the climax of "Showdown, Part 2" is awesome, no clear explanation is given about how [[spoiler:Ben got Feedback back during his fight with Malware; he gets eaten by Malware, has a vision of his past self with which to reconcile his issues about losing Feedback, and then suddenly regains said form even though it was made perfectly clear that the Omnitrix could ''never'' get it back]]. The scene is frankly a huge DeusExMachina.
* AuthorsSavingThrow: This series has been said to attempt to reconcile the conflicting styles of the first ''Ben 10'' series by Man of Action and the two sequels by Glen Murakami and Dwayne [=McDuffie=]. So far, [[BrokenBase fans are really disagreeing about whether they succeeded or not]].
** A question a few fans nagged about was why the Plumbers were working again in the sequels when they were retired in the first series, plus all of the alien members despite being an Earth force. "Malefactor" explained that after the first series, they decided to reinstate the Plumbers.
* BadassDecay: While he has his LetsGetDangerous moments, Ben is still portrayed as much more bumbling and less competent in this show than he was in the two previous sequels, and has a bad tendency to be turned into a ButtMonkey. Partially justified due to his lack of familiarity with the new Omnitrix, but still extremely irritating.
** Arguably, the new "perfect" Omnitrix compared to the "prototype" versions. It lacks certain useful features that the Ultimatrix had (e.g. instant knowledge of all alien powers upon transformation), and it seems to backfire more often than even the first Omnitrix did in the original series. Additionally, it apparently now has "glitches" that remove entire powers from certain aliens.
*** Actually, WordOfGod states that any "malfunctions" are [[http://www.formspring.me/DerrickJWyatt/q/349394956424593959 entirely Ben's fault,]] which can occasionally be seen when Ben dials the wrong alien and then transforms without bothering to see if he's actually selected the one he wanted.
**** This explanation can work for the wrong transformation, but not to explain why the time limit is shorter than before, or the fact it lacks some functions. Plus, it implies [[WhatAnIdiot Ben is too stupid to actually check what alien he is using]]. [[SarcasmMode Yeah, that's much more satisfying...]]
* BaseBreaker: Bloxx. Some fans think he is an original, delightfully weird alien and raise him to EnsembleDarkhorse level. Other think the idea of a Franchise/{{LEGO}}-based alien life form seems silly and doesn't make any sense, even in the ''Ben 10'' universe.
** For similar reason, Liam and his Omnitrix counterpart Kickin Hawks are either considered hilarious or completely stupid.
** While Rook has indisputably become an EnsembleDarkhorse, there are some fans who still feel like he is a CanonSue SpotlightStealingSquad who make Ben's incompetence painfully obvious. Not helped by the fact the series itself points out how Rook has been saving his butt quite often. He gets gradually better as the story goes on, though.
** Khyber is either a CreepyAwesome EgomaniacHunter, or a generic villain who relies on his dog to fight his foes. This division of opinion seems to have subsided by "Of Predators and Prey", where it's revealed that [[spoiler:he was hired by Malware and he is ''not'' the BigBad as thought]].
** Blucik and Driba are, depending which part of the fandom you ask, hilarious ComicRelief or incredibly annoying {{Creators Pet}}s who cause more problems than they solve.
** Ben himself, some frustrated at what they feel is serious character degradation and his lack of maturity, others are either okay or just don't care about it.
* BrokenBase: Fans who prefer the [[WesternAnimation/{{Ben 10}} original series]] are waaaaay more hyped for it than fans of [[WesternAnimation/Ben10AlienForce the]] [[WesternAnimation/Ben10UltimateAlien sequels]].
** You can divide them that way: Original ''Ben 10'' and/or Derrick Wyatt's fans who are glad to see the show going back to its original roots and become "fun" again, and ''Alien Force''[=/=]''Ultimate Alien'' fans who are afraid Wyatt might be removing everything brought by the sequels (including the good parts) for the sake of going back to the original show. The fact he confirmed several sequel episodes would be CanonDiscontinuity and hinted several times he wasn't really a fan of the sequels ''doesn't'' help.
** And then there are those who still believe in the original series only and see both ''Alien Force'', ''Ultimate Alien'' and ''Omniverse'' as crappy.
** While many aliens' designs ''had'' been criticized in the ''AF/UA'' era, especially later ones like Eatle, Jury Rigg, and Fasttrack, many others were already good to begin with, raising some controversy about the point of redesigning them as well (especially the original series aliens, whose designs were critically acclaimed for most anyway). Most notable examples of those unnecessary redesigns include Fourarms now having a mustache and Big Chill being now a bulky bug instead of a skeleton-like skinny creature.
** The theme song; some are glad the show gets an actual song with lyrics instead of an instrumental piece again, others feel it's overly childish, even compared to the original show's one;
** The ContinuityPorn, particularly the flashback around 10 years old Ben; a lot of fans are glad about it, since it brings back an original series feeling; others feel that it's a bit forced and unnecessary (what's the point of trying to make 15 years old characters more like their original selves if their original selves will show up in flashback episodes on regular basis anyway?) and will only end up wasting episode that could have been focusing on the plot.
** [[MagicalDatabase Primus and the Codon Stream]] being retconned; while many fans who disliked the concept are glad it's gone, others are mad it was just classified CanonDiscontinuity and point out this creates only more plotholes.
** The fact the show is privileging a DenserAndWackier approach and RuleOfFunny over a good plot also is starting to bother a lot of fans, especially the return of Ben's ButtMonkey status.
* CharacterRerailment: While overall the same character, Zombozo lost his supernatural aspects in favor of a much more standard clown gimmick in ''Ultimate Alien'', seeming more like SelfDemonstrating/TheJoker. This show brings back those supernatural aspects, though in a way that accurately reflects his name (he looks more like a decomposing corpse, complete with flies circling his body and his ribs being able to be seen, rather than the vampire the first series presented him as). Partially failed in that he also gets a wackier personality and a smaller role that makes him less creepy and threatening than he was in his previous appearances.
** Intended with 15 years old Ben, but much like in season 3 of ''Alien Force'', the result is... [[TookALevelInDumbass deba]][[BaseBreaker table]]...
*** "Malefactor" and episodes later on seem to be attempting to downplay his ButtMonkey, BookDumb, and {{Jerkass}} qualities, taking a much higher ground in morality, becoming serious when the situation actually calls for it, and managing to come up with plans on the spot. Ben, as a result, hues much closer to both his first series self and his sequel self. Then he got back to be an idiot in later episodes.
** Eon's design is portrayed as closer to his movie self. Considering many thought the ''Ultimate Alien'' version actually was cooler than his movie self, whether it's a good thing or not is up to debate. With that being said, he's much more like a [[CompositeCharacter mixture]] of the various versions, taking the basic backstory of the ''Ultimate Alien'' incarnation ([[spoiler:[[FallenHero he's Ben]] according to WordOfGod]]) as well as threat level, and the movie incarnation's appearance.
*** Interestingly, there are also aspects of his movie self that were present in UA but left out here, most notably his ''entire head.'' It's like UA used half of Movie Eon's design, and Omniverse uses the half that UA ''didn't.''
* ComplainingAboutShowsYouDontWatch: Many people don't want to watch the show because they don't like the new human designs.
* CompleteMonster: Malware has basically turned into this, and even goes as far to destroy [[spoiler:Feedback]] and later, [[spoiler:Galvan B]].
* ContestedSequel: Let's face it; with the already BrokenBase caused by the two previous sequels, this show was ''doomed'' to be this before it was even up.
* ContinuityLockout: Perhaps inevitable, considering the fact that the show references elements and brings back threats that haven't been seen in a long while (Megawhatts, a ''one-off'' threat from the first series), as well as coming right after two of the most arc-oriented entries in the franchise.
* CreatorsPet: Feedback in the eyes of some fans; he is introduced as being Ben's favorite alien when he was 11, despite the original show clearly establishing Fourarms as Ben's favorite in the original series era. Few reasons about why Ben likes him so much are given, when him simply saying he is "cool and awesome" or mentioning "he felt like he was a part of me." Still, he is quite popular with fans, so the trope might be partially averted. [[spoiler: It turns out that he was ''getting addicted'' to that form, though.]]
** Also, Blucik and Driba; Derrick Wyatt has mentioned that the team adores them, that their episode "Blucik And Driba Go To Mr. Smoothies" is a favorite amongst them, and that he wouldn't mind them having their own show. However, a lot of fans feel like they are just annoying, and their episode was a big waste of time.
* DieForOurShip: Esther is either bashed by Ben X Julie / Ben X Gwen / Ben X Kevin fans, or praised by Ben X Julie bashers.
* DudeNotFunny: The whole episode "So Long And Thanks for the Smoothies" is played for laugh, but some fans weren't really amused with what its ending implied. See the FridgeHorror section for more details.
** Ben being back to his immature ButtMonkey status wasn't that funny for a lot of fans, who feel it more like BadassDecay than anything else.
** Not to mention Ben and Julie's breaking up ''being a gag.''
* EarWorm: A first since the original series, ''Omniverse'' has a song[[note]]a song is a musical piece that specifically has lyrics, and thus is meant to be sung[[/note]] and not an instrumental piece. And it's extremely catchy.
* EnsembleDarkHorse: [[HypercompetentSidekick Rook]], big time. Ironically, he was initially seen as a ReplacementScrappy for Kevin and Gwen, but as soon as trailers and later episodes revealed his status as an {{Adorkable}} BadassNormal NiceGuy, his popularity amongst fans raised considerably. By now, he is the main reason why many skeptic fans gave a chance to ''Omniverse'', and most haters consider him the best thing coming out of the show.
** Extremely variable depending of which part of the fandom you ask, various new aliens are either liked, hated or shrugged, but Feedback seems to have got quite popular.
** Shocksquatch's redesign made him a lot more popular, [[CreatorsPet even among the crew]].
** Princess Looma, the {{Yandere}} alien in love with Ben.
** Attea also seems to be rather well-liked.
* EpilepticTrees[=/=]{{Fanon}}: It's popular fan theory that Ben forgot to include Primus from the Universal Rebuild in "So Long And Thanks For All The Smoothies," as DerrickJWyatt says that, pursuant to the [[ExecutiveMeddling mandate that continuity be "cleaned up,"]] whatever that means, meaning that it no longer exists. The universal rebuild has in fact been used to explain ''everything'' that is different about this series from the previous one.
* EsotericHappyEnding: "Frogs of War" ends with [[spoiler:Attea taking over the Incursion Empire and leaving her father in custody to the Plumbers]], which is portrayed as an acceptable ending. The kick is that both Alien Force and this show etablished that [[spoiler:Attea is ''much'' crazier and aggressive than her father (keep in mind that in her first episode, she wanted to blow up Earth ForTheEvulz, while her father just threatened to do it because he wanted to find her). And now, [[OhCrap she is the one in charge]].]]
* EvilIsCool: Khyber generally got good reception for this.
** To an extent, Malware as well, especially after "Trouble Helix" revealed his backstory. [[spoiler:And then it turns out he got a design change and he's the actual BigBad...]]
** ''Psyphon'' manages to actually be incredibly BadAss in the second episode. His appearance in "Outbreak" may only increase this, as [[spoiler:he gets to become half-Pyronite]].
* EvilIsSexy: Attea; despite being from a race of frog aliens that looks rather ugly by human standards, [[CuteMonsterGirl she actually is quite attractive of her own]]. It does help that SheIsAllGrownUp compared to how she look in Alien Force.
* FanDumb: Just in case complainings from ''AF/UA'' fans weren't enough, there are also some original series fans who already hate this show just for taking place in the same continuity of the previous sequels.
** Remember all those plotholes and retcons that made fans cry that ''Alien Force'' and ''Ultimate Alien'' sucked? Yeah? Well don't expect the same fans to complain when ''Omniverse'' does its own even more confusing retcons or makes blatant SeriesContinuityError{{s}}; apparently, it's okay if it's against ''AF[=/=]UA''.
* FashionVictimVillain: Dr. Animo's costume as the Ant-King. Probably intended.
* FoeYay: Attea and Ben; it starts with him asking her (though as a joke) if she will turn into a princess if a guy kisses her; then as the show goes on, she grows more and more obsessed with fighting him personally, to the point she [[TheOnlyOneAllowedToDefeatYou forbids her forces to attack him]]. And to sell it completely, [[spoiler:she ''actually'' falls for Bullfrag, his Incursean form, to the point she offers him to come with her at the end]]. The 'kiss' on the cheek at the end, though, was with Ben ''as himself.''
** Ben and Vilgax get a little ''too'' cozy with each other in "Vilgax Must Croak". Taken UpToEleven when Vilgax does a DivingSave and ''saves Ben's life''.
-->'''Ben''': Did you just do what I think you did?
-->'''Vilgax''': I uh... I don't know what came over me...
* GrowingTheBeard: "Malefactor" and afterward starts to tone down Ben's ButtMonkey tendencies and [[CharacterRerailment fix the characterization problems he's went through]], the pacing slows down, drama somewhat increased, and addressing the complaint that [[SpotlightStealingSquad Rook sometimes severely outshines Ben]] by showcasing a few episodes with Ben solo or at least with a different partner.
* HilariousInHindsight: In 2010, there was a short-lived Franchise/{{LEGO}} ''Ben 10'' line based on ''[[WesternAnimation/Ben10AlienForce Alien Force]]''. Now there's Bloxx, an alien who's actually ''made'' of LEGO bricks.
** Also, when Rook can tell that Ester likes Ben, Ben doesn't believe it and responds by saying "'cuz you know everything about girls!" Turns out he does, especially when Ben realized Rook had a girlfriend.
* HoYay: With Kevin gone, Rook has become the main character yaoi fangirls can pair up with Ben. Not helped by the fact that 1) he admits himself to be an AscendedFanboy of Ben, 2) he has been revealed to be of a ''[[CatBoy feline species]]'' and 3) he actually seems to dislike Esther when she flirts with Ben...
** Certain episodes are absolutely chock full of homoerotic undertones. Special mention goes to "Bros In Space". For a bit of context, the whole episode revolves around Rook's father not approving of Rook's choices--bringing Ben to Revonnah being among said choices--and as a result, it's overflowing with a "why don't you like my boyfriend" sort of vibe. The cherry on top has to be when Rook snubs Rayona, his ex-girlfriend whom he supposedly still has feelings for, because he "does not yet know the plans of [his] houseguest", AKA Ben.
* IAmNotShazam: The villain featured in the episode "Trouble Helix" is Malware, ''not'' Helix, despite the name of the episode. Helix is the name of the device that was used to create him.
* InternetBackdraft: Kevin's new appearance in this show has garnered a ''lot'' of hatred from Kevin's {{fangirl}}s. In fact, one of them even [[http://fc07.deviantart.net/fs70/f/2012/340/7/2/fans_opinions_about_kevin_new_design_by_silverlady7-d5n8aqp.jpg wrote a list of all insults used by fans to describe said new look.]] And that includes many fans who actually ''like'' ''Omniverse''.
** And let's not even talk about what happened when it turned out Gwen got a ''second'' redesign.
* ItsTheSameNowItSucks: There have been criticisms about the show reusing ideas or concepts from the original show, resulting in repetitive parts (such as episode whose scripts seems to be ''[[RecycledScript directly based on original show episodes]]'') or ContinuityPorn that doesn't make much sense (cameo of the Kraken, a creature that wasn't portrayed as an alien in its first appearance, as used by space pirate for a watchdog, or a cameo in present of Exoskull, a villain from '' five years in the future at least'').
* JerkassWoobie: [[spoiler:Even though Phil was a bastard in his only original show appearance, ''Omniverse'' revealed that, after surviving for a year in the [[PhantomZone Null Void]], he ended up captured by Malware and Psychobos, used as a test subject for the Nemetrix, sent after Ben, apparently gravely injured due to the Nemetrix being unable to function right with him, and then took by his captor ''again''. God knows what they did to the poor guy after that.]]
** Malware ''sort of'' started out as this, but, once Albedo "cured" him, [[SubvertedTrope threw the Woobie part out the window]] uses all his next appearances to [[KickTheDog show us]] [[TheSociopath what a bastard he really is]].
** Ben 23 gets this treatment too. In "Store 23" we first see Ben 23 as ''more'' of a narcissist than the original Ben. Then we learn that [[spoiler: in this universe, Max died before Ben received the Omnitrix. Without Max, there's no CharacterDevelopment that helped the original Ben become the hero he is today and no one by Ben's side. All the money and fame he receives in the universe will never replace family, treating 23 Ben more as a StepfordSmiler.]]
** Hell, the original Ben may qualify [[spoiler: when Feedback's DNA is killed right in front of him by Malware.]]
* [[JustHereForGodzilla Just Here for Rook]]
* LoveItOrHateIt: Fans either love ''Omniverse'' for taking the show back to its roots, making many homages to the original show and giving [[EnsembleDarkhorse Rook]], or hate it for its overly simplified art style, juvenile tone, and decayed Ben.
* [[MagnificentBastard Magnificent Bitch]]: Attea, full stop. [[spoiler:The whole Incursean story arc was a plan from her to take over her Father's throne.]]
* MisBlamed: Quite a few fans blame Derrick Wyatt for the DenserAndWackier nature of the show, but this was actually due to ExecutiveMeddling. Since the original series always gets the best ratings, the execs wanted ''Omniverse'' to go for a tone closer to that series, making Wyatt insert a goofier and way more light-hearted tone and style.
* MoralEventHorizon: Malware either crossed it either by murdering several Galvanic Mechamorphs in "Trouble Helix" (sure, he needed to feed himself, but he shows no remorse, and is actually mad because [[ItsAllAboutMe Azmuth cures them instead of helping him]]) or by [[spoiler:using Phil as an unwilling test subject]].
** He definitely crossed it in "Malefactor", when he decides to keep Ben from pursuing him by ''[[WouldHurtAChild throwing a tanker truck at a school bus]]''.
** [[spoiler:Ben 23]], of all people, almost crosses it by [[spoiler:attempting to ''rip his dimension's Azmuth in half'']]. He is fortunately stopped before this happens.
** Dr. Psychobos crossed it when he came up with a plan to [[spoiler:assassinate Azmuth and ''commit genocide'' on the entire Galvan species.]]
*** If the above didn't count for Malware, helping Psychobos do ''that'' [[spoiler:''to his own species'']] certainly does for him as well.
* NightmareFuel:
** Zombozo's new, corpse-like design, which, if you look closely, you can see his ''ribs'' and some flesh that appears to be falling off of his body on his face.
** Malware really upped the ante by [[spoiler:forcibly tearing young Ben out of Feedback while he was in that form, then brutally killing said form [[MoralEventHorizon simply to spite Ben]]]].
* {{Narm}}: In "Many Happy Returns", Looma mocks Gwen by calling her a "girl", causing her to act like if her BerserkButton had been pushed and turn Anodite to attack Looma. If you think for a second, the scene doesn't make any sense, considering both characters are girls, and no explanation is given about why Gwen reacts this way.
** Unless Looma meant the insult as in [[JustAKid "girl"]] instead of "(young) woman" (which, seeing as Gwen is a teenager in college, would be more appropriate), but even that explanation is flimsy.
* NightmareRetardant:
** While the concept of a DoomsdayDevice able to destroy the whole universe is quite scary, it's a bit hard to take it seriously when it's called "Anihilarg."
** Trumbipulor tries to invoke NightmareFuel with his robot minions by designing them on the scariest, most threatening-looking creatures he could think of in the galaxy. The problem is, he is afraid of ''mice'', which aren't exactly considered scary by human standards.
* {{Padding}}: In "Frogs of War Part 1", the Randomizer function seems to have been added to the episode just to give a problem to Ben, as it doesn't really add a whole lot to the episode considering Ben's problems and frustrations with the Omnitrix ''already'' (common problems include the time limit's varying length and changing into the wrong alien a lot), and takes up a few minutes in the least. The Omnitrix could have glitched out and there really wouldn't have been much of a difference.
* PanderingToTheBase: The show as a whole is obviously intended to satisfy all the original series ''Ben 10'' fans that complained about ''Alien Force'' and ''Ultimate Alien'' being too different; as a result, we get characters being redesigned to look closer to their original series selves, several characters and elements from the original series coming back (including one-off characters such as the Megawatts), and flashbacks parts and episodes taking place in the original series era. O, and Kevin and Gwen are PutOnABus, possibly to satisfy those who complained about RomanticPlotTumor. Well, at least they didn't try to satisfy the [[KissingCousins Bwen]] fans...
* ReplacementScrappy: Rook has been initially seen as this to Gwen and Kevin by some fans (though fans who considered Gwen and Kevin [[CreatorsPet Creators' Pets]] and disliked [[RomanticPlotTumor Gwevin]] were a fair bit more accepting of him) before the series came up. By now however, he has become [[EnsembleDarkhorse the opposite]].
* RescuedFromTheScrappyHeap: Some of the poorly designed aliens from ''Ultimate Alien'', such as Jury Rigg and Eatle, got a bit of this thanks to their new designs. Jury Rigg's aviator suit, especially, made him only more popular.
* TakeThatScrappy: Ben finally gets called out for his arrogance in "Predators and Prey Part 1" by Rook, who can't stand it at this point, a sentiment that many fans have felt since ''Omniverse'' began. While part 2 revealed that it was a charade, he ''seriously meant what he said to Ben about his arrogance''.
** And according to WordOfGod, [[http://www.formspring.me/DerrickJWyatt/q/410836306784971342 he is not too fond of]] [[ReplacementScrappy Fastrack]], which explains the increase of the usage of [=XLR8=].
** Probably unintentional, but those amongst the fans who dislike Blucik and Driba might enjoy this part of dialogue from "Store 23":
--->'''Azmuth''': "You two are brilliant scientists."
--->'''Blucik and Driba''': "Oooooooooh!"
--->'''Azmuth''': "By Earth's standards; for a pair of Galvan, you are remarkably unintelligent."
--->'''Blucik and Driba''' (''disappointed''): "Oooooooh...."
** The ShipSinking of Ben/Julie came with Ben unintentionally hurling insults at Julie while playing a video game. The fact that Julie was so unpopular with the fandom couldn't be a coincidence.
** Will Harangue getting "accidentally" sprayed by Ben using Water Hazard just when he's starting to go on yet another tangent.
* TearJerker: The reason why Ben doesn't use Feedback anymore.
* TheyChangedItNowItSucks: Some fans are already acting this way:
** The fact Kevin and Gwen will no longer be part of the cast didn't please Gwevin shippers (or for the matter, those who liked the characters).
** While most alien redesigns were more or less well-received, the ''human'' redesigns have outraged fans by being even more simplified than the ones from ''Alien Force''. Ben's new haircut and mouth, Kevin's face and Gwen's redesign after she went to school are the most panned.
*** Some alien redesigns haven't been so well-received; Big Chill being bulky instead of his original scrawny skeleton-like design, Fourarms' mustache, Spidermonkey's {{Wolverine}}-like hairdo, and Alien X's LanternJawOfJustice, displeased some fans. Not helped by the fact Big Chill was a major EnsembleDarkhorse in ''Alien Force''.
** The Omnitrix no longer possessing the traditional faceplate (at least not visible on the outside) that had been kept in all forms of the Omnitrix (including the Ultimatrix) also raised anger amongst fans.
** Gwen having freckles (even her 10 years old self, despite the fact she never did in the original show) was also badly received. Believe it or not, some fans were outraged by it.
** Ben's [[{{Flanderization}} new]] [[TookALevelInDumbass personality]] is unpopular amongst several fans.
** Some fans ''really'' took badly Derrick Wyatt stating he intended to undo Charmcaster's partial HeelFaceTurn. Though to be fair, he was speaking ''hypothetically'' --- there's as good a chance that she won't end up in ''Omniverse'' at all, since she's evidentally a hard character to get down in the show's style. And if she does, the partial HeelFaceTurn won't be "undone" so much as [[RetGone never happened.]]
** While initial new aliens like Crashhopper or Bloxx got good receptions, most of those introduced in "Outbreak" (The Worst, Molestache...) were criticized by some fans for lazy designs and names, and many fans would have rather seen previous aliens coming back instead of new, useless {{Joke Character}}s.
** For a character who had been for a long time considered as a [[TheScrappy Scrappy]], there actually are a large amount of fans who are mad about Julie not showing up anymore.
** The excuse of "Omnitrix glitches" used by DJW to remove powers from aliens is considered lazy by some fans, and some of them aren't happy it removed powers such as Goop's HollywoodAcid.
* TheyWastedAPerfectlyGoodCharacter: Gravattack is the only one of the new aliens that can do something ''none'' of Ben's aliens could do before; he also is one of the least used aliens so far.
** The Vreedle Brothers; after the CharacterDevelopment they got in UltimateAlien and their HeelFaceTurn, the writers decided that they were better as villains and just had them blow up the Plumber Academy before being back to being Con Men. Especially annoying in that this was totally unnecessary: if they wanted villainous Vreedle Brothers, they could have just used a separate pair of clones that were still criminals, seeing how ''Con of Rath'' etablished there were an army of them.
** Julie was starting to get better as a character and had been RescuedFromTheScrappyHeap thanks to both CharacterDevelopment and the fact she TookALevelInBadass. Instead of keeping going this way with her in order to improve her again, the writers decide to have Ben and her break up off-screen (with the break-up being shown as a flashback) and introduce a new character as Ben's love interest. The final nail in the coffin? WordOfGod is that ''Omniverse'' will go beyond 60 episodes now...and there are no plans for Julie to appear in ''any'' of these planned episodes at all. She's been PutOnABus, possibly for good.
* TheyWastedAPerfectlyGoodPlot: "So Long and Thanks for the Smoothies" involves Ben and Rook trying to prevent a DoomsdayDevice from falling into the wrong hands, and ends with Ben using Alien X to rebuild the universe. A lot of fans feel the whole thing would have been much better as a serious series finale, or if at least the characters had to deal with the changes caused by such a major event (''à la'' ComicBook/InfiniteCrisis). Instead, we get a random comical episode that has seemingly few to no impact on the story. The only change made was a new design for the Mr. Smoothy store that Ben loves to visit and that it "doesn't taste the same."
** Actually, Mr. Smoothy's was far from the only thing that got changed. This episode is the reason for '''all''' the changes and {{Retcon}}s that follow in the show, a result of Ben not being experienced enough with Alien X's powers to recreate the universe exactly as it was before. Of course, the comical downplaying of this still makes this a prime candidate for this trope regardless.
*** That [[{{Fanon}} was never stated in the episode]], and there ''are'' changes and retcons that appeared before that episode.
** As of "Showdown, Part 1," Psychobos and Malware's plans for the Nemetrix amounted to using it as a glorified distraction. Khyber alone has it now, but as far as the other two's purpose for it, it's largely disappointing. As a matter of fact, Malware is able to pull out his plan of his own ''without using the Nemetrix a single time'', making you wonder why they worked so hard during five years to complete it when just recruiting bounty hunters or killers to distract Azmuth would have worked just as fine.
** In "Showdown Part 1", they introduce the natural predator of the Galvans. Due to its avian nature, some fans believe that it should have been a peacock, using Ben's fear of them to it's advantage. It wasn't.
** Khyber hacking the Plumbers' database for information about Malware in "Trouble Helix", as well as the fact he helps Ben and Rook in "Malefactor" suggested he was a DragonWithAnAgenda who intended to conspire against Malware at some point. This is never brought up in later episodes, or at least not farther than him being obsessed with getting Ben as a trophy.
*** Talking about Khyber, it had been suggested in previous episode that he actually [[EvenEvilHasLovedOnes cared for his pet]], a theory fans liked to support. The writers apparently feared this would lead to DracoInLeatherPants, so they had Khyber [[YouHaveOutlivedYourUsefulness leaving]] [[KickTheDog said pet behind]] in the finale, despite the fact it was entirely against his advantage (see WhatAnIdiot below), completely dropping the idea.
** "Showdown Part 2" has the protagonists of all four series ([[TheHero Ben]], [[BadassGrandpa Max]], [[MagicalGirl Gwen]], [[TheAtoner Kevin]], and [[HypercompetentSidekick Rook]]) coming back and teaming up altogether to stop Malware. How do they do so? By splitting up immediately for various tasks, with Ben fighting Malware alone, Rook and Gwen merely acting as pilots and assistant to Azmuth, Max helping Blucik and Driba to repair a station (by giving up his beltbuckle, no less), and Kevin doing absolutely ''nothing'', instead just having a short subplot where he befriends Khyber's pet. In the end, we don't get any stand of all of them against Malware, who Ben defeats on his own, with the sole help of the Galvanic Mechamorphs and Azmuth. Talk about making Ben's friends even more useless in a fight than they were in ''Alien Force''...
** The show establishes that aliens are a well-known fact among the public, and that they can walk among the populace peacefully. This could have been potentially used to develop issue about FantasticRacism and how the population is adapting to this. However, the story usually doesn't do anything with the idea, usually just showcasing Ben's interactions and treating everything as if nothing's changed. The lack of use of this idea may have even resulted in [[SeriesContinuityError a particularly bad, somewhat grating continuity error]], where "The Frogs of War" reveals them to the human race for the first time, despite previous episodes, seasons, and series contradicting this as Earth has been attacked by aliens several times now.
* UncannyValley: Fistina's face in "Special Delivery" when she gets a date. Seriously.
* UnfortunateImplications: [[http://images4.wikia.nocookie.net/__cb20130128205426/ben10/images/7/71/Julie_OV_2.jpg Julie's new design]] looks more caricatured of Asians than her previous design did.
** Talking about Julie, it's revealed in ''Rule of Engagement'' that her and Ben broke up... but Ben didn't know it. And yet, several episodes taking place prior this one had him flirting with girls and considering pursuing relationships with them, basically implying he was ''cheating'' on Julie and didn't see anything wrong with it.
** In ''Frogs of War'', Blucik and Driba, when fighting Psychobos, explicitly state that "the dumbest Galvan is smarter than a Cerebrocrustacean". Apart from the fact it [[BrokenAesop nullifies what Azmuth stated in "Showdown Part 1"]], this makes it sound like they are [[NotSoDifferent just as racist as Psychobos is]].
* WhatAnIdiot: If you think about it, Khyber really didn't need to leave his pet behind when he escaped in "Showdown Part 1"; since the Nemetrix works only on non-intelligent beings, that means he will have to find a new pet to replace it and train it to obey him. Moreover, Azmuth would have used the pet to track him had Malware not distracted them.
** Yeah, Dr. Psychobos, we know you are a genius, but do you seriously believe the shapeshifting kid who saved the universe a billion times isn't a threat to your plans?
*** You ''really'' don't want to [[BullyingTheDragon push your dragon around]] when said dragon is ''[[EgomaniacHunter Khyber]]''.
** Almost ''everything'' [[TooDumbToLive Blucik and Driba]] do enters in that territory, the cake probably being when they leave their duties to go look for a Mr Smoothie while the Plumbers are in the middle of a crisis.
** Ben treats putting Vilgax in Incarcecon rather casually. He's survived several incidents where he was supposed to be dead and has come closest to getting the Omnitrix. As pointed out by Max, Ben should be the first to know Vilgax is not to be underestimated. [[spoiler:Ben ultimately pays for this at the end of the episode, where Vilgax gets away.]]
*** [[spoiler: Though this may be partially justified [[VillainDecay due to how he was in]] ''[[WesternAnimation/Ben10AlienForce Alien Force.]]'' [[TookALevelInBadass Though, one then wonders why he was so casual about it]] [[WesternAnimation/Ben10UltimateAlien when one remembers what]] [[DidYouJustScamCthulhu happened the last time he met with him.]]]]
** The very reason Ben broke up with Julie is because of Ben's complete stupidity. Seriously, what kind of complete moron would keep playing video game while his girlfriend is talking to him at the phone?
*** If that wasn't bad enough, Ben never ''once'' considers to call her when she stops contacting him after the event, yet still considers Julie to be his girlfriend as of "Rules of Engagement." That's... [[Series/StarTrekTheOriginalSeries illogical]], to put it lightly.
* WTHCastingAgency: In a nutshell, any time they bring back an old alien but find a new voice actor to play him.
* WinBackTheCrowd: The show has been trying to recapture the magic of the first series. [[BrokenBase Reactions have varied.]]