Ultimate Kevin

Here are the mutations Kevin suffered in the Ben 10: Ultimate Alien.

Ultimate Kevin
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 misshapen chaotic amalgam form of the creatures of the Ultimatrix. This form, dubbed Ultimate Kevin, is very powerful and easily defeated Ultimate Aggregor and drained his powers. However, Kevin's personality has become even worse than it was in the original series.

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 of his sanity, as he spared an opposing Gwen. Either way, Kevin was too powerful for anyone to beat and Ben thought "putting him down" was the best option.

In Absolute Power, Kevin's self-control is almost entirely overtaken by his insanity. His Osmosian instincts have caused him to develop an insatiable hunger for energy and begins draining the life force of anyone unfortunate enough to cross his path, regardless of whether or not they had powers. 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 puts her own life at stake and tries to help Kevin by talking. He reveals to her that he still had a single shred of his humanity that let him stay away from Gwen, knowing that his remaining willpower would be overwhelmed by his insanity and that he would end up draining her if he got the chance. Ultimately, despite his love for Gwen, Kevin is overwhelmed by his hunger and he ends up partially draining her of her life force and powers, nearly killing her. He then becomes obsessed with her overwhelming amount of energy and ends up tracking her over the rest of both episodes (though his feelings for her prior to his mutation become mixed with his insanity, as seen when he commenting that he thinks she's deliberately avoiding him and how he shows anger when Cooper tries to stop him from killing her and tries to kill him as well).

Ultimate Kevin was cured in Absolute Power: Part 2, thanks to the efforts of Ben, Gwen, Cooper, and Darkstar. However, Darkstar becomes Ultimate Darkstar 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 power to their rightful owners as well as reviving the five Andromeda Aliens.

In Night of the Living Nightmare, Ultimate Kevin appeared in a dream, trying to convince Ben to surrender the Ultimatrix.

Appearance

 * Kevin Levin: Hair; Clothing.
 * Big Chill: Wings; Hood.
 * Brainstorm: Two legs in place of lower left arm.
 * Chromastone: Right Shoulder Crystals.
 * Diamondhead: Right Arm Structure.
 * Four Arms: Torso; Body Shape; Arm Count.
 * Goop: Body Structure.
 * Humungousaur: Torso; Chest Plates; Tail.
 * Ultimate Humungousaur: 1/4 Face.
 * Jetray: 3/4 Face; Skin; Right Foot.
 * Lodestar: Left Shoulder Spike; Right Hand.
 * Rath: Upper Left Arm; Left Foot; Left Wrist Claw.
 * Spidermonkey: Lower Right Arm.
 * Ultimate Spidermonkey: Lower Jaw.
 * Swampfire: Left Arm Structure.
 * Water Hazard: Water Ports.
 * Terraspin: Body holes.

Powers and Abilities
Kevin has his own and the abilities of all the aliens of Ben Tennyson. Here's the list of the abilities that are shown.
 * Kevin Levin: Power Absorption.
 * AmpFibian: Electrokinesis; Flight; Electric Absorption.
 * Armodrillo: Earth Eruption, Earth Tremors, Jackhammer Arm; Enhanced Strength.
 * Big Chill: Flight; Ice Breath; Intangibility.
 * Brainstorm: Electrokinesis.
 * Chromastone: Ultraviolet Beams; Energy Absorption.
 * Diamondhead: Shapeshifting Arm; Diamond Projectiles.
 * Echo Echo: Sonic Screams.
 * Four Arms: Enhanced Strength; Enhanced Durability; Enhanced Jumping.
 * Goop: Liquefaction.
 * Humungousaur: Enhanced Strength; Enhanced Durability.
 * Ultimate Humungousaur: Enhanced Strength; Enhanced Durability.
 * Jetray: Neuroshock Blasts; Space Survivability.
 * Lodestar: Magnetism.
 * NRG: Energy Blasts.
 * Rath: Wrist Claw.
 * Ultimate Spidermonkey: Web Spit.
 * Swampfire: Flame Projection, Chlorokinesis.
 * Terraspin: Tornadoes; Aerokinesis.
 * Heatblast/Alan: Pyrokinesis
 * Nanomech: Bioelectricity; Minor flight
 * Water Hazard: Hydrokinesis.
 * Ultimate Aggregor: Jackhammer Arm; Enhanced Durability; Hydrokinesis; Energy Blasts; Electrokinesis; Flight; Space Survivability; Aerokinesis.
 * Gwen Tennyson and Stone Creatures: Mana Manipulation; Mana Sensing; Mana Absorption.