Kevin Levin

Kevin Levin or Kevin Ethan Levin, is a half Human /half Osmosian with the ability to absorb any type of energy or matter and release it at will. He first appeared in the original series, and quickly became one of Ben's most notable nemeses. However, he reformed in Ben 10: Alien Force, and then became one of the main hero characters.

Ben 10
Kevin is first encountered by Ben in an arcade, where, after befriending him, he was assaulted by bullies and saved by Ben as XLR8. The two attempt to steal video games from a warehouse and get caught by the police, forcing Ben to reveal his powers to him in order to escape. Eventually, Ben breaks off their partnership when Kevin rigs two trains (one carrying money and one carrying people) to collide, not caring that hundreds of innocent people would be killed. Ben became Heatblast to stop Kevin, but to even the odds, Kevin grabs onto Heatblast and absorbs his powers, changing him into an incomplete version of Heatblast. When Ben foils Kevin's plans and escapes, Kevin leaves to use his new powers to get revenge on the bullies that picked on him. But Kevin's new powers disappear and changes back to his regular form. When Ben shows up as Fourarms to stop Kevin, Kevin absorbs Fourarms' power and changes into an incomplete version of Fourarms. As Ben and Kevin fight, Ben gains the victory and offers Kevin a new home and a chance to be a good guy. Kevin accepts, but Ben realizes he lied and Kevin tries to take the Omnitrix off of Ben, but feedback from it changes Kevin back to normal and appears to be depleting his powers. He escapes and at the end of the episode reveals he still has Heatblast's powers.

Kevin serves as the main antagonist of the second season. His ability to project heat at the end of Kevin 11 is a result of the Omnitrix's feedback pulse: the amount of energy it emitted allowed him to fully absorb its powers, giving him access to every alien form Ben had at the time. However, because Kevin's ability to regulate this power is poorer than that of the Omnitrix itself, the energy suppresses his human form and forces him to remain as an alien most of the time:

As revealed in Framed, Kevin blamed Ben for this, so he used the powers of the Omnitrix to start a crime spree in Los Angeles, both for his own benefit and to damage Ben's (or rather, his alien forms') reputation. Eventually, Kevin's ability to regulate the power fails altogether, causing him to permanently mutate into what Vilgax would describe as a "misshapen, chaotic amalgam of creatures from the Omnitrix." This form has: Fourarms' head, body, left eyes, legs and feet, Grey Matter's right eye, Upgrade's upper back, Heatblast's left arm, Diamondhead's right arm, Wildmutt's arms below them, XLR8's tail, Stinkfly's wings, Ripjaws' antenna, gills, and teeth and Ghostfreak's black lines running along his chest.

Because of this, Kevin fights Ben and as he was about to kill him, Lt. Steel from the Special Alien Capture Team shoots him into the water and is presumed dead, but at the end of the episode, he is revealed to be alive because the water bubbled which meant he was breathing because he had Ripjaws's ability to breathe underwater.

After his mutation, Kevin gloats that he has all of Ben's powers plus his own, making him Kevin 11"(the name' Kevin is credited under in the ending sequence of the show). He has Stinkfly's ability to fly and his slime spitting. Diamondhead's diamond ability with his right arm. Fourarm's strength. Wildmutt's sniffing ability. XLR8's speed. Heatblast's ability to shoot fire out of his left arm. Ripjaw's bitting and unhingeable jaw(possibly also his ability to breath under water because he has Ripjaw's gills), and Upgrade's laser vision. Although Kevin does not have all of the powers of the Omnitrix aliens he copied. He does not have Grey Matter's intelligence, Upgrade's ability to take control machines, and Ghostfreak's ability to turn invisible and his ability to walk through walls. Despite Kevin's claim, Ben notes that Kevin's powers are only one-tenth as strong, as seen when Diamondhead was able easily catch and crush with his bare hands, the Petrosapien projectiles Kevin fired at him (This assestment is proven correct in Ultimate alien as Aggregor stated that when Osmosian's absorb the life force of other beings they only gain 1/10th of that being's powers) and Kevin never exhibits his original power in this form.

Ben 10:Alien Force
Kevin comes back in Ben 10: Alien Force, where he was eventually released from the Null Void (he stated in Darkstar Rising that he did his time for his crimes) returned to his human form, and reconcilied with his family. He has also become an alien weapon dealer, giving him several contacts with criminals (such as Argit, Vulkanus and Sunder the Retriver) as well as a considerable knowledge in alien tech. He has also come back to his human form and gained the ability to absorb solid matter.

Ben 10:Ultimate Omnitrix
He is a same character as his Alien Force version.