Kevin's Mutations

Kevin's mutations are caused by Kevin's power of absorbing energy, and absorbing energy from Ben's aliens and from the Omnitrix/ultimatrix itself. The result of this was a mutation consisting of a conglomeration of all of Ben's aliens.

Original series
At first, in the original series, Kevin simply absorbed power from one alien at time, earning the abilities of those aliens. Later when he and Ben were fighting, Ben walked away causing Kevin to get angry and turn into a mutation creatures of the Omnitrix, which Kevin dubbed the form Kevin 11 (due to having the 10 aliens from the Omnitrix and his own powers). Kevin was quite powerful in this form, but only had, or showed, the abilities of the aliens most obvious in his of all ten of Ben's aliens. While, as Vilgax put it, a misshapen chaotic amalgam ofform of the creatures of the Omnitrix and they weren't as strong as Ben's pure versions. However, he is capable of mixing the abilities to his advantage, such as using Heatblast's flames and Stinkfly's goo to form an explosive attack, which was Ben's idea. Kevin also proved strong enough to hold his own against Vilgax in a fight, which Ben was incapable of.

After years in the Null Void, his human DNA overwrote the alien DNA, causing Kevin to lose this form in the Alien Force timeline but in the Ben 10,000 timeline he'd keep absorbing alien DNA, becoming Kevin 11,000, who is most likely non-cannon.

In the Ben 10,000 timeline, he had a son, Devlin Levin who could could transform into Kevin 11.

In the Ultimate Alien episode, ...Nor Iron Bars a Cage, it is revealed how Kevin changed back to normal from this mutation. When he becomes a prisoner after being trapped in the Null Void, he was met by another prisoner named Kwarrel, who Kevin soon came to help for. Kwarrel taught Kevin how to control his anger and powers. Soon enough, Kevin becomes sane again, and returns to his human form.

Appearance:
 * Four Arms' frame, arm count, left eyes, legs, head, and torso
 * Heatblast's upper left arm
 * Stinkfly's wings
 * Upgrade's upper back
 * Diamondhead's upper right arm
 * Ghostfreak's track
 * Grey Matter's right eye
 * Wildmutt's lower arms
 * Ripjaws' lure and teeth
 * XLR8's tail

Abilities:
 * Four Arms: Super strength
 * Heatblast: Fire blasts
 * Stinkfly: Flight, Slime spit
 * Diamondhead: Shapeshifting arm, Crystal shards, Invulnerability
 * Wildmutt: Sense of smell
 * Ripjaws: Breathing underwater, Steel-bending jaws
 * XLR8: Super speed

Alien Force
In Vengeance of Vilgax, while Ben was trying to hack the Omnitrix, the Omnitrix overloaded. Kevin tried to help Ben by trying to override the system, but instead he got blasted by the feedback that the Omnitrix created. He turned into a mutation of every solid material he had ever absorbed (Stone, Metal, Copper, and Taedenite). Fortunately, he could generate spikes, hammers, and blades from his arms.

In Trade-Off, Kevin teamed up with Darkstar to turn back to normal. He succeeds but lost his powers, making him least useful to the team. Gwen finds out what he did and goes after Darkstar. Darkstar then absorbs all of her power, and Kevin realizes the only way to save her is to stop Darkstar. After the fight with Darkstar, he got his ugly mutation back (so did Darkstar), and Gwen was saved.

In Time Heals, Gwen tried to turn him back to normal by going back in time and stopping the disaster, but later learned that it had to happen after Charmcaster made Kevin a rock slave.

He turned back to normal in The Final Battle: Part 2 when the Omnitrix is destroyed in battle. According to Max, the Omnitrix kept him in that form.

Ultimate Alien
In The Forge of Creation, in order to stop Aggregor from absorbing the powers of a newborn Celestialsapien, Kevin had no choice but to absorb the Ultimatrix's powers and turn into, as Vilgax would call it, a a misshapen chaotic amalgam form of the creatures of the Ultimatrix. This form, dubbed Ultimate Kevin, is very powerful, and very quickly and easily defeated Ultimate Aggregor before draining him of his powers. However, Kevin's personality has become even worse than it was in the original series. This form doesn't seem to have the same set-back as the first mutation, 1/10 of the alien's powers.

Throughout ...Nor Iron Bars a Cage, The Enemy of My Enemy, and Absolute Power, Ultimate Kevin goes rampant on attacking people who either owed him or he wanted revenge on. Fortunately, Kevin still seems to have some control his sanity, as he willing spared an opposing Gwen. Either way, Kevin is too powerful for anyone and Ben thinks "putting him down" is the best option.

In Absolute Power, he goes more insane and tries to rob the powers of other beings. Ben still thinks that eliminating Kevin once and for all would be the best choice. Gwen, however, sees that the power is controlling Kevin's mind. Gwen deliberately tries to help Kevin by talking, though it has no use. Gwen later teams up with Darkstar to defeat Ultimate Kevin by stripping his powers using a Dominus Librium fragment.

Ultimate Kevin was cured in Absolute Power: Part 2. However, Darkstar becomes Morningstar again by absorbing the powers from the Dominus Librium which had absorbed Kevin's powers. Fortunately, Ben anticipated this from the beginning and presses a button which not only strips Morningstar's new powers, but returns the abilities to their rightful owners as well as reviving the five Andromeda Aliens.

Appearance:
 * Four Arms' torso, arm count, back and legs
 * Jetray's right foot, half of his face, upper back, right eyebrow, eyes, and mouth
 * Diamondhead's right arm structure
 * Spidermonkey's lower right arm
 * Big Chill's blue cloak/wings and antennae
 * Swampfire's left arm structure
 * Lodestar's left shoulder spike
 * Humungousaur's chest and tail
 * Half of Ultimate Humungousaur's face
 * Chromastone's crystals on his right shoulder
 * Two of Brainstorm's legs in place of a lower left arm and right claw (Diamondhead's skin)
 * Rath's left claw, left hand (Swampfire's skin), left foot (Jetray's skin)
 * Water Hazard's water ports
 * Ultimate Spidermonkey's split lower jaw(Jetray's skin)

Abilities:
 * Kevin: Matter and Energy absorption
 * Swampfire: Fire blasts, Seeds, Chlorokinesis
 * Humungousaur: Super strength
 * Ultimate Humungousaur: Super Durability
 * Big Chill: Ice breath, Flight, Intangibility
 * Chromastone: Light beams, Energy absorption
 * Brainstorm: Electric blasts, Forcefields, Telekinesis
 * Jetray: Nueroshock blasts
 * Goop: Liquification, Stretching
 * Rath: Wrist claw
 * Diamondhead: Shapeshifting arm, Crystal shards
 * Water Hazard: Water blasts, Invincibility
 * Armordrillo: Jackhammer arm
 * Terraspin: Aerokinesis, Twisters
 * NRG: Radioactive laser, Heat generation
 * AmpFibian: Levitation, Electricity
 * Echo Echo: Sonic Scream
 * Ultimate Spidermonkey: Web spit
 * Lodestar: Magnetism
 * Alan Albright/Heatblast: Pyrokinesis
 * Gwen/Rock Monsters: Mana blasts

Possible future
In the episode Ken 10, which takes place in one of the possible futures, Kevin escapes the Null Void with the help of his son Devlin and declares that during his time there, he absorbed the power of all other aliens trapped with him, becoming Kevin 11,000.

Appearance:
 * Heatblast's torso, right tentacle, legs, left wing(all colored black), head flame, and shoulder flame
 * Four Arms' body frame, feet and left arm
 * Ghostfreak-esque skull-like face
 * Wildmutt's lower arms
 * Upgrade-patterned tentacle jutting out of the left forearm, tipped with the pattern from XLR8's tail, black coloration on Heatblast parts
 * A Null Void Guardian's tentacles and Heatblast tentacle right arm
 * Stinkfly's wings
 * Diamondhead-based right wing
 * Benwolf's sonic howl

Abilities:
 * Shifting from Kevin to Kevin to Kevin 11,000
 * Flight
 * Shapeshifting arm
 * Sonic howl
 * Super strength

Pyronite DNA


Kevin is mutated in this form after absorbing some Pyronite's DNA from Ben in the form of Heatblast, when Kevin wanted to crash two trains, one filled with passengers and the other filled with money that he wanted to steal, so Ben attempts to stop him as Heatblast but Kevin sneak behind him and absorbs Heatblast's DNA.

Kevin looked like an incomplete version of Heatblast, having a different face, one of his arms mutated and part of his chest while displaying Heatblast's pyrokinetic abilities.

Tetramand DNA


Kevin is caused by this mutation with DNA Tetramand when Kevin goes with his new powers. As the form of Heatblast, Kevin goes to the bridge where the gang lived bothered him while Ben and the others travel there to prevent this from doing something stupid, Ben comes before and Four Arms while Kevin absorbs Four Arms DNA. The mutation left Kevin with a face different from Fourarms, a human eye, Kevin's hair, above the 2 arms wide and nail, 4 additional human arms.

Magic Monster Rock
It is not known exactly when Kevin takes this form, this happens in the Time Heals, it is believed that Kevin was somehow pressed to absorb one of the Rock Monsters used by Charmcaster, thus giving Charmcaster and Hex total control over Kevin, making him their slave and unwillingly fight Gwen and Ben as Spidermonkey

After ignoring Professor Paradox's warnings about Time-traveling, Gwen changes the future by preventing the hacking of the Omnitrix and the mutation of Kevin, but after succeeding and returning to her timeline, she sees what could happen in the future if the accident had never occurred, making Gwen rearrange everything again back to the way it was.

Kevin changed his appearance to having rock skin, purple eyes and having Charmcaster's Rock Monsters lines and markings "imprinted" over his body.

Trivia

 * Kevin's mutations appear to be an Osmosian trait (which he inherited from his father Devin Levin) as the full Osmosian villain Aggregor is shown to be capable of absorbing & assimilating alien DNA which allows him to gain their abilities and causes a slight mutation (though nowhere as extreme as Kevin's). It is possible that Kevin's mutations are a result of this ability, however Kevin may be unable to control his mutations either due to inexperience and possibly due to him being only half-Osmosian (though Kevin 11,000 has shown the ability to retain certain alien abilities he has absorb while in human form, such as XLR8's super speed).
 * Kevin's alien mutations seem to have the frame of four arms (red, bulky, and four sets of arms).
 * Each of Kevin's mutations have a unique trait to them before/after being cured
 * 1) After being cured from his first mutation, his clothes are completely intact
 * 2) His second mutation destroys his clothes completely (except his briefs). This isn't undone upon being cured like the first mutation
 * 3) His second mutation is the only one in which he retains his original body frame
 * 4) His third mutation, unlike the first, doesn't restore his clothes. Also, only Kevin's pants remain intact