History YMMV / Ben10UltimateAlien

* RealismInducedHorror: "Catch A Falling Star" is considered one of the creepiest episodes by fans due to the actions of Carl Nesmith/Captain Nemesis being PlayedForHorror in a realistic way. He semi-emotionally manipulates Jennifer Nocturne and exploits her MadLove for him to escape prison, [[DisproportionateRetribution seeks revenge on Ben for upstaging him as a hero and beating him in a supposedly friendly competition]], and actually commits murder in the episode (he kills a plastic surgeon after he changes his face offscreen and is shown killing a driver who only wanted to help him). Jennifer's StockholmSyndrome is also called to attention, due to having suffered from ParentalNeglect that led her to run away to become a celebrity and also made her grow attached to Nesmith despite the fact that he kidnapped her and endangered her, all because she's desperate for affection.

** Sunny seems to have a mixed reception. She's either considered to be a fun EvilCounterpart and an effective rival to Gwen or an obnoxious, one-dimensional character who adds nothing to the story and her also, her designs are considered to be lazy and uninspired.

* MemeticLoser: Even though the show tries to fix Vilgax's VillainDecay, he still regains this status thanks to the [[spoiler: [[AntiClimaxBoss incredibly lackluster fight he had with Ben]] and the [[{{Narm}} unintentionally funny line]] "You stabbed me!"]]. As a result, there are some fans who still don't take him seriously.

** Also, [[spoiler:Jennifer Nocturne developed StockholmSyndrome, even to the point of having feelings for Carl Nesmith (Captain Nemesis)]]. Five months later, Creator/KristenStewart, whom Jennifer Nocturne is an {{Expy}} of, [[spoiler:cheats on Robert Pattinson, having a brief affair with director Rupert Sanders]]. Boy, did the show predict what would happen to Kristen Stewart...

** The amount of times that Ben and Gwen think they've either stopped or defeated Kevin in "Absolute Power" Parts 1 and 2 (the second season finale) is this because it makes absolutely ''no'' sense why they think someone as strong as him (remember, he'd absorbed Ben's Omnitrix alien forms' powers, the aliens Aggregor had absorbed in season 1, the Plumbers Helpers' alien powers, Doctor Viktor's, and a bit of Gwen's) would be defeated by their (relatively) weak attacks and the episodes keep having small time-wasting moments of both of them being stupid and not just knocking Kevin out while they're ahead, letting him easily get back up, or escape their traps until Ben ''finally'' fully does it near the end of Part 2 so they can do their plan. It just comes off as pointless filler and the characters acting dumb when they're not ''supposed'' to be doing so. It also ruins the pacing of them a bit.

** Weirdly [[FutureBadass Ben 10,000]] does this too '''himself'''. Unlike his incarnation in [[WesternAnimation/Ben10 the Original Series]] Ben's future self doesn't transform at all instead having access to all his abilities in human form, with there being no physical differences. For all the complaints ''Omniverse's'' take on Ben's future self would receive, having him physically transform again is agreed to be a universal improvement.

* WTHCastingAgency: Creator/FredTatasciore not reprising his role as Cannonbolt, despite voicing a few characters in the episode that introduced Ultimate Cannonbolt.

* EvilIsSexy:
** Aggregor is the first ''WesternAnimation/{{Ben 10}}'' BigBad to not be a hideous monster and actually be reasonably attractive, with long hair and an open shirt too.
** Also, [[spoiler: Hive Elena]]. A very dangerous version of RavenHairIvorySkin.

** Will Harangue is basically a [[Franchise/SpiderMan Jonah J. Jameson]] {{Expy}}, the only real differences beside his look being that he is an anchorman instead of a newspaper director and pursuing Ben, a character created by Man of Action, instead of Spider-Man. A few years later come ''[[WesternAnimation/UltimateSpiderMan2012 Ultimate Spider-Man]]'', which Man of Action is working on... and Jonah J. Jameson is portrayed as an anchorman instead of a newspaper director. Later adaptations of ''Spider-Man'' would go to further this take, mainly the MCU films and the [[VideoGame/SpiderManPS4 PS4 game]] and its sequels. Even funnier enough, the games would later ''also'' cast Yuri Lowenthal in the titular role and the first would feature his wife in a secondary role.

** The fight between Ben and Gwen was supposed to be a dramatic moment as their arguements about Ultimate Kevin hit it's lowest points, but Ben shouting his alien names can make the situation unintentionally humorous.

** For some viewers, Gwen's cousin Sunny became this by the end of the episode she appeared in [[spoiler: due to [[TheScrappy Grandma Verdona]] vocally favoring Gwen over her ''right in front of her!'']]

*** Ripjaws was an AlluringAnglerfish with MoreTeethThanTheOsmondFamily in the original series, Here, he has a more catfish-like face and fish lips that may have been an attempt to make him less NightmareFuel-y. However, fans weren't pleased ''at all'' and Derrick promised repeatedly that his ''Omniverse'' design would be much cooler and closer to his original design (and it was).