Vilgax's return in Ben 10: Alien Force season 3 had him trying to take over Earth by challenging Ben to a legally-sanctioned gladiator match between the two that awards the winner control over the planet. The fan outcry about Vilgax suddenly caring about honor and laws seemed odd for the usually lawbreaking Evil Overlord and after thinking about the end of season two, I realized there were two very good reasons for Vilgax to take this route.
First off, Ben had recently helped to save the galaxy from destruction, in addition to giving the Highbreed a way to save themselves from their genetic decay. He has the gratitude of entire alien species, as attested by the mound of medals he keeps in his closet, and is also best buds with the Highbreed Supreme Commander. Even if Vilgax was actually able to kill Ben, he'd have to deal with massive backlash from the rest of the galaxy and a race of beings that have a far larger fleet and no qualms about wiping him out. Alternately, if he attacked Earth with an invasion fleet and Ben called for help, the Highbreed would back him up. Ben takes the Power of Friendship to new levels and Vilgax is smart enough to realize this.
Second, it also happens that every time Ben and Vilgax have tangled in the past, he's had help from his family and allies like Azmuth, Tetrax and even his future self. Vilgax has pumped himself up with bionics and threw a robot army at Ben, but lost because he had other people to encourage him, save his butt or unlock a new power for him. Vilgax has to know at this point if he's going to beat Ben, it has to be one-on-one and it may be he wants to be the one that kills the one sentient being that's caused him more trouble than anything else in the universe. That's why he defeated the other world's champions so he could take their powers and weapons to add to his own, it was to match the diversity of the Omnitrix's forms. If he defeated Ben in fair & legal combat, he would be safe from reprisals and have ownership of the Omnitrix, the item that started the whole rivalry with the Earth boy in the first place and which will give him the edge he needs to conquer the Universe. It's not Diminishing Villain Threat, It's Personal and smart. —koolkame
As a person who likes Alien Force, thank you so much for this! It makes re-watching the fight even sweeter without Diminishing Villain Threat hanging around.
Regarding the multiple powers and weapons to match the Omnitrix aliens bit, that's also why Vilgax is often being referred to "Conqueror of 10 Worlds"; it's to mirror the abilities gained from those conquests to the alien forms of Earth's champion, Ben 10.
If Ben beat Vilgax in a duel to decide who owns earth, doesn't that make him in charge of Earth?
Yes but only in the eyes of the rest of the galaxy and universe; people on earth do not acknowledge it however.
Gwen and Kevin, strangled by the red string? Maybe. Or maybe it's what happens when a slightly education-obsessed nerd girl starts trying to hook up with a Jerk With A Heartof Gold whose affection for his ride puts the "car" in Cargo Ship. Kevin is heavily implied to have had a bad home life before he mutated in Ben 10 and lavishes way too much attention on his car to be considered healthy, Running Gag or not. Gwen's love life isn't really brought up, but anyone who takes someone to task about why they haven't asked her out does not seem too knowledgeable about flirting. It hit me that of course they would have a mixed-up chemistry since these are two people who have probably avoided relationships for fear of being hurt (Kevin) or because their focus is on higher learning and are separated by their intellect (Gwen, who is attending a prep school). I never saw the red string snag because I had already classified them as a textbook case of Opposites Attract, not terribly original but still a classic combination. It does make the few times they really connect all the more poignant like the season two finale where Kevin calls Gwen back from going full Anodite even if it meant she could save the universe or their dance at the end of "Save the Last Dance". —koolkame
Remember too that both had more than likely felt separated from "normal" society from a younger age, so more than likely had felt uncomfortable getting close to other people, leaving them disaffected with the possibility of finding love, or even feeling a close connection with most people. —Kittyhawk
On the topic of Kevin, we learn in Vendetta that his father was a Plumber killed on duty, there's a possibility that his step-father (as he mentioned Devin as "My real father" one time) was likely abusive toward him for being part alien. Add that with the hint dropped about the frequent use of his powers (as his father used his energy absorption powers, he seems glad "nothing happened this time" after using it subsequent times) especially being eleven years old and suddenly his Troubling Unchildlike Behaviour is quite justified. Unfortunately, it leads to a bit of Fridge Logic in that Max Tennyson, who was with Devin at the time of his death and was asked to take care of his son, had to not have recognized him in order to justify not explaining to Ben why he was acting the way he was. - Metal Shadow X
Re-watching "Kevin 11" answered this problem for me because Max never sees Kevin in his human form except for a brief moment at the end IIRC. It's possible Max thought that it was another Osmosian boy or his hiding of his Plumber past made him keep quiet about knowing Kevin's family; heck, Max lied to his WIFE about being a Plumber and it's likely Devin Levin did the same with his son. Plus, the bad effect of absorbing energy for Osmosians pretty much explains Kevin's change during the Time Skip: if Devin was worried about a one-time use of energy absorption, Kevin's near-constant use could not have been healthy for him. Think back to Kevin's baggy eyes in Ben 10 and he becomes the PG version of a young junkie with the Alien Force Kevin being on the rebound from addiction. -Nice Retcon, MacDuffie - koolkame
Back to Kevin; why did he perform a Heel-Face Turn in the first place back in Alien Force? Because a Plumber sacrificed himself to save him. Why was it that simple? Because someone already did the same thing to help him escape the Null Void. Someone who helped him return to his human form and whose death he felt he was responsible for. Understandably, that bit of tragic deja-vu was all it took for him to reform. - Metal Shadow X
In addition to that, his father was a Plumber who died in the line of duty. That must have caused a crisis of conscience for Kevin when the Magister died to save him and his possessiveness of his badge takes on a whole new meaning afterwards - koolkame
In Alien Force, I was kind of skeptical when it turned out the Master Control also gave Ben access to all of the aliens in the Omnitrix. At first I thought, "Well that's pretty cheap, the Master Control didn't do that in the original Ben 10". Then I realized... who's to say it didn't? The original series episode where Ben unlocked the Master Control was before "Ben 10,000", and therefore before Ben had any idea how many aliens were in the Omnitrix, and before he'd seen any forms like Spitter or Articguana and learned they were in the Omnitrix. He's not going to try and transform into something if he doesn't know it's there, now is he? Then I thought, "Wouldn't he have noticed when he was scrolling through the dial that he had thousands of new forms?", only to realize that Ben, being an excitable 10 year-old who'd just been given the ability to mentally switch forms, probably never even looked at the dial after unlocking the Master Control! - Khfan429
Also, based on how Ben zeroed out the master control at the end of season two, it seems like merely turning the dial gets rid of the feature. He was most likely being careful that he didn't mess it up earlier.