Vilgax (Classic)

Vilgax is an intergalactic alien conqueror, a Chimera Sui Generis who serves as Ben's archenemy and is the most recurring villain in the franchise. He was introduced in And Then There Were 10, and has since appeared in all the seasons of the original series (however the only season 3 episode he appeared in was Ben 10,000), as well as season three of Alien Force.

Personality
Vilgax is ruthless, cruel, and power hungry. His primary objective seems to be gaining the Omnitrix so that he can use it to take over the universe. He is known to be very manipulative, notably so of the Galactic Code of conduct, in order to achieve his goals. While stranded on Earth following his defeat at the end of Alien Force, Vilgax skillfully manipulates a group of humans known as the Flame Keeper's Circle into serving him. Upon dicovering that his squid-like form resembles the alien of knowledge worshipped by the cult, he adopts the role for his own and manipulates his new followers into helping him escape the planet.

Despite his cruel and villainous tendencies, Vilgax does care about his own people (taking his role as Vilgaxia's ruler and champion very seriously), so much so that he is willing to put his own life on the line and use whatever other means necessary to ensure Vilgaxia's, and its people's, safety; even if it means begging his enemies for help.

Background
A vicious galactic warlord known as "the most dangerous being in the universe" Vilgax's goal is to get the Omnitrix and use it to create an army capable of transforming into any alien to conquer the universe. Though he originally chased Ben only because of this, and had few concern about his fate once he would get the Omnitrix, the several failures the boy caused him, as well as an imprisonment in the Null Void, causing his hatred for Ben to grow, so much that, in his last appearances, he seems to want to kill him nearly as much, if not more, as to get the Omnitrix.

Vilgax is one of the most feared beings in several galaxies, having conquered ten planets, destroyed five others and created a black hole. In fact, he is so feared, that almost no biological lifeform is willing to work for him, forcing him to use robots for his entire crew, though he is able to find mercenaries willing to work for him for the right price.

Original Series
Vilgax first appeared in And Then There Were 10, where he is seen shooting at Xylene's ship to recover the Omnitrix, forcing Xylene to throw it down to Earth and causing the main plot of the series. His limbs were both destroyed because of the battle, causing him to be placed by his drones in a repair tank for healing, where he stayed for most of season 1.

As the series progressed, Vilgax soon discovered the Omnitrix had been taken by someone else (though ignoring exactly who it was), and made several indirect attempts to get the device back. This includes sending robots from his ship, hiring bounty hunters Tetrax, Kraab and Sixsix and turning Earth's criminal Joey into the cyborg Rojo by fusing her with one of his drones. In the latter, he was able to shortly establish a telepathic link with Ben when the boy was fused to Rojo as Upgrade, warning him he was going to come for him one day.

Eventually, his body was repaired and cybernetically enhanced in Secrets, making him far taller and stronger than before. He then went on Earth to get the Omnitrix by himself. Ben's aliens proved to be no match for him, and Vilgax captured him. Though surprised to see the one who had caused him so much problems was just a human child, Vilgax revealed him his plan for the Omnitrix, and attempted to extract the Omnitrix from him, seemingly by sectioning his arm with an alien tool. After several complications, including interruption from Gwen and Max and Ben losing control of his transformations, the Chimerian Hammer exploded, seemingly with Vilgax still aboard.

In Truth, Max tells Ben and Gwen how he had a run in with Vilgax who was stealing warheads from a military base when Max and his partner Phil showed up. In the resulting fight, Vilgax was strapped to a warhead by Max, and launched into his own ship. At that time, Vilgax was only slightly larger than a human man, compared to his now colossal size (an addition to his cybernetic augmentation).

Vilgax appeared in the non-canon episode Gwen 10, where Ben re-lived the day he found the Omnitrix, only for Gwen to find it instead. Unlike the first episode, Xylene's ship self-destructed and Vilgax wasn't hurt. After the drone failed to retrieve the Omnitrix, he went to get it himself and succeeded to capture Gwen, later being overpowered by Max and Ben. Max later threw Vilgax into the Hammer as Upgrade, seemingly killing Vilgax.

At the end of the second season, Vilgax is still alive, having survived the destruction of his ship by teleporting out just before the explosion, but being frozen as a result. He is found encased in ice by Kevin. Discovering Kevin's connection with the Omnitrix, Vilgax decides to team up with him in another attempt to retrieve the Omnitrix, however both are locked away in the Null Void dimension by the end of the episode.

A dream version of Vilgax appears in the episode Perfect Day, where he appears to confront Ben. The battle lasts for a short time, and then Vilgax tries to send Ben to the Null Void. As Fourarms, Ben throws him in instead, but this proves to be an error on the part of the Forever Knights, as Vilgax was about to send Ben to the Null Void without first obtaining the Omnitrix. It is the same reason why Ben found out that the battle with "Vilgax" is just a set-up.

Vilgax appeared in another non-canon episode Goodbye and Good Riddance, where he threatens Carl's life, forcing Ben to reveal his secret by transforming into Cannonbolt. At the end of the episode, Ben lures Vilgax into the underground bus line and Carl activates the fire system, incinerating Vilgax.

Vilgax reappears in Ben 10: Secret of the Omnitrix, where he once again attempts to retrieve the Omnitrix, having somehow escaped the Null Void (the enhanced version of Secret of the Omnitrix revealed that he stumbled on a Null Void portal being opened and used it to escape). During a flashback, Tetrax reveals that Vilgax destroyed the Petrosapien's home world, and he (Tetrax) unwittingly gave Vilgax the final element needed to carry out his plan. Vilgax refers to his anger at having been trapped in the Null Void (including showing a short nervous twitch at its mention), which has deepened his grudge against Ben to the point where he refuses to acknowledge the danger threatening the universe if the Omnitrix self-destructs (but nevertheless gains enough respect for Ben to the point of calling him by his first name instead of his last name). He confronts Ben on Tetrax's ship and attacks him, only to be shot out into space through the airlock. He is finally defeated when Azmuth, the creator of the Omnitrix, gives Ben access to a massive alien, Way Big, who hurls Vilgax into outer space.

Ben 10: Alien Force
Vilgax returns in Ben 10: Alien Force season 3, having come back in a currently unknown way. His appearance has changed again; he is less cybernetically enhanced and his mouth is visible again. In addition to his traditional army of drones, he has been joined by new alien assistant, Psyphon. In order to justify his invasions, he now follows a Galactic law, fighting champions of a planet he attacks and defeating them to gain the right to legally conquer that world. In this manner, he conquered ten worlds, the last of which was Ultimos', and absorbed the champions' powers with the help of Psyphon, giving him powerful, new abilities. Despite all of his new found power, Vilgax retains his obsession with the Omnitrix.

After his victory against Ultimos, Vilgax returns to Earth, where he quickly defeats Max and the Plumbers' kids. He does not however, choose to absorb their powers and instead uses them as messengers to Ben, challenging him in the rules of the Galactic Code, as he did with his other conquered planets, and leaving him 24 hours to answer, after which Vilgax will enforce his legal right to destroy Earth. After accidentally overloading the Omnitrix and recollecting his escaped aliens, Ben comes and fights him. After a long and feral bout, Vilgax eventually smashes Ben as Chromastone to pieces, seemingly killing him. However, as Vilgax is about to take the Omnitrix, it reformats Chromastone's remnants into Diamondhead, bringing Ben back to life. Due to both his age and the practice he had with this form during summers, Diamondhead proves to be strong enough to defeat Vilgax, and the Galactic Conqueror, according to the laws, is forced to leave Earth with his army and never come back. He begrudgingly accepts his defeat, but vows to get revenge on Ben one way or another.

Although Vilgax is manipulating the rules of the Galactic Code (which were established by the peaceful Galvans to prevent the massive loss of live) for an evil purpose, he does follow through on his adherence to them, despite his plan back firing.

In Ghost Town, Vilgax breaks Ghostfreak out of his prison in exchange for the secrets of the Omnitrix. However, Ghostfreak betrays him and invades his homeworld, Vilgaxia, by possessing the majority of its inhabitants and turning them in Ectonurite slaves. After vainly fighting the invasion, Vilgax escapes and reluctantly asks help from Ben and his team. After an uneasy alliance between them, they eventually reached Ghostfreak, and Ben let himself be possessed in order to absorb him back into the Omnitrix. Though it was successful, Ghostfreak took over Ben's personality, resulting in a battle between Ben's team, Vilgax, and himself (the former two parties now in contension over whether or not Ghostfreak should be harmed while in Ben's body). Vilgax was eventually able to produce enough light to weaken Ghostfreak, allowing Ben to take over again and turn back to human form. Vilgax then allows his Ben, Gwen, and Kevin to leave, having earned their freedom for their help. Vilgax later gloats to himself about having aquired the secrets of the Omnitrix.

In the episode 40 of Alien force, Vilgax attacks the planet, Primus, causing the Omnitrix to teleport Ben, Gwen, and Kevin to the world as well. The Omnitrix leaves Ben's wrist to find Azmuth. Azmuth uses the Omnitrix himself to fight Vilgax & protect Primus. Vilgax defeats Azmuth and takes the Omnitrix from him. As the device has recalibrated since he last operated it, Vilgax no longer knows how to do, forcing him to ask Ben for the information in exchange for his friends' lives (after taking them captive).

Ben activates the Omnitrix, turning Vilgax into Goop, but Ben steals the artificial gravity disk and turns it off; leaving Vilgax as an immobile puddle. Ben takes the Omnitrix out of the puddle of Vilgax as Goop, changing Vilgax back to normal and then re-attaches the device to himself. Ben as Cannonbolt throws Vilgax into the Codon stream (which is full of the DNA the Omnitrix accesses to transform its wearer) where he grows considerably larger. Ironically, at the end of this episode Ben throws Vilgax into space after changing into Way Big similar to Vilgax's defeat at Ben's hands 5 years prior. It has been revealed by Dwayne McDuffie that this was intentional. Some time after, Vilgax returns to his usual size.