Ultimate Aggregor

Ultimate Aggregor is Aggregor's mutation, formed when he absorbed the abilities and forms of five powerful aliens he hunted down from the Andromeda Galaxy (P'andor, Galapagus, Andreas, Ra'ad, and Bivalvan) in order to become strong enough to search for and reassemble the four fragments of the Map of Infinity, the one item capable of leading him to his goal, which was to get to the Forge of Creation and absorb the powers of an infant Celestialsapien (which he refers to as the "Ultimate Prize") to gain unlimited power and rule the universe.

Appearance
Aggregor went through a mutation similar to that of Kevin Levin, become an amalgamation of various characteristics from his absorbed targets - his new identity was known as "Ultimate Aggregor." However, unlike Kevin, Aggregor's appearance is more refined and balanced, as opposed to Kevin's random and mixed placement of alien organs - a result of a special machine he used, as Aggregor's powers have the full potency of his victims' energy. His mixed body parts were comprised of the hands and legs of Bivalvan, the front torso of Galapagus (though with a darker color), the unarmored back of Andreas as well as his arms, P'andor's faceplate on his neck, and seal on his chest, and a head resembling that of Ra'ad. His eyes became blood-red and his height increased to roughly ten feet.

Personality
Ultimate Aggregor is a cruel, sadistic, menacing and remorseless sociopath, who does whatever it takes to achieve his goals, having no remorse for any of his actions. His intelligence is extremely high and his plans go to very great lengths to succeed - as shown when he managed to trick Ben Tennyson and his team into retrieving the fragments of the Map of Infinity for him. He fears no one and hungers for power.

Unlike most of Ben's other enemies, such as Vilgax and the Highbreed, Aggregor prefers to carry out his plans himself instead of trusting his robotic minions to do the work, instead using them for lesser duties, such as maintenance, manual labor, security, and being cannon fodder against his enemies.

History
By the end of Ultimate Aggregor, Aggregor used the Entropy Pump to transfer the powers and abilities of the five aliens into himself. Humungousaur managed to stop the pump before it destroyed reality. Unfortunately, it was too late as Aggregor had completely absorbed the five aliens, transforming into his mutated state, a massive chimeric mutant, named Ultimate Aggregor.

Continuing in Map of Infinity, Humungousaur, enraged that he was unable to save the Andromeda aliens, viciously attacked Ultimate Aggregor, demonstrating Humungousaur's incredible strength. Unfortunately, Humungousaur's attacks did near nothing to Ultimate Aggregor he was invulnerable as Bivalvan's armor. Thanks to Galapagus, Ultimate Aggregor was immune to Gwen's mana attacks. Showing off his newly acquired powers and abilities, Ultimate Aggregor toyed with Ben's team and easily defeated them all, greatly damaging Grandpa Max's nervous system in the process. After knocking Humungousaur out with a powerful seismic strike that destroyed a lot of Los Soledad in the process, Ultimate Aggregor left, now able to travel through space on his own. Azmuth then reveals that the reason Aggregor absorbed the aliens was so that he had the power to find the four fragments of the Map of Infinity, which will allow him to enter the Forge of Creation and obtain the greatest power in the universe. In order to stop him, Ben and the others must keep him from getting at least one of the fragments. After going through a temple filled with booby traps on Mykdl'dy, a fire/ice planet, Ultimate Echo Echo and the others nearly reach the first piece, but due to Four Arms and Kevin being forced to hold up the door that leads to the chamber holding the piece and Gwen being hit by a poison dart, they were powerless to prevent Ultimate Aggregor (who used the trio to discover the traps and lead him to the first fragment) from escaping with the first fragment of the map.

In Deep, Ultimate Aggregor invaded the core of Piscciss to steal the second piece of the map, which was in the form of the planet's anti-gravity generator. With the ocean planet falling apart, Ultimate Big Chill had no choice but to save Piscciss and let Ultimate Aggregor escape.

In Where the Magic Happens, the trio chased Ultimate Aggregor to the Door To Anywhere, which Ultimate Aggregor used to enter Ledgerdomain. Gaining the assistance of Charmcaster, the trio entered Ledgerdomain. When the group was in a battle with Adwaita, Ultimate Aggregor used it as a diversion to attack Adwaita from behind and steal the Alpha Rune from him, the third piece of the map, before thanking Ultimate Humungousaur for helping him and teleporting away. With only one more piece left, Ben becomes more determined than ever to stop Ultimate Aggregor.

In Perplexahedron, Ultimate Aggregor travels to the Perplexahedron, which was built by Paradox to protect the fourth piece of the Map of Infinity. He uses the map's other pieces to enter the Perplexahedron and makes his way through it, where he encounters Gwen and leaves her to freeze in a snow room. He finally makes it to the fourth piece but has a battle with Ultimate Cannonbolt. Despite his best efforts, Ultimate Cannonbolt is beaten and loses the final piece to Ultimate Aggregor, who escapes the crumbling Perplexahedron, now able to enter the Forge of Creation. Despite losing the battle for the map, Ben and the others vow to stop Ultimate Aggregor once and for all.

In The Forge of Creation, Ultimate Aggregor attacks Ben, Young Ben, Kevin and Gwen in the Forge of Creation and easily defeats Gwen and Kevin, leaving the Bens to fight him. Ultimate Swampfire grows vines to hold Ultimate Aggregor in place while Young Stinkfly attacks him. Ultimate Aggregor breaks free and knocks down Stinkfly, who transforms back to Young Ben. He knocks out Ultimate Swampfire, who turns back to Ben. Young Ben offers his Omnitrix to Kevin to absorb it and fight Ultimate Aggregor, but Kevin refuses and absorbs the energy from the Ultimatrix. Ultimate Aggregor enters the egg and prepares to absorb the Baby Celestialsapien, but is stopped by Ultimate Kevin, towering above Ultimate Aggregor. Ultimate Kevin attacks Ultimate Aggregor and absorbs him, reverting Ultimate Aggregor back to Aggregor and leaving him unconscious.

Powers and Abilities
Ultimate Aggregor had access to all of the five aliens' powers combined.
 * Andreas' enhanced strength, durability, and shockwaves.
 * Bivalvan's invulnerability and hydrokinesis.
 * Galapagus's immunity to mana and aerokinesis.
 * P'andor's radioactive energy projection, heat generation, and immunity to heat/cold.
 * Ra'ad's electricity manipulation, mind reading, flight, and the ability to breathe underwater.

He is also invulnerable to Gwen's mana attacks.

Weaknesses
Ultimate Aggregor was harmed by Max's plasma pistol and Ultimate Cannonbolt's attacks.

Ultimate Aggregor was harmed by Jetray's neuroshock blasts, Swampfire's fire blasts and Brainstorm's electric blasts. Ultimate Aggregor was trying to absorb the attacks, but couldn't, due to his lack of skill.

Ben 10: Ultimate Alien

 * Ultimate Aggregor (first appearance, cameo)
 * Map of Infinity
 * Deep
 * Where the Magic Happens
 * Perplexahedron
 * The Forge of Creation
 * The Ultimate Enemy: Part 2 (flashback; cameo)

Etymology
Aggregor's name comes from the word "aggregate", which means to form a collection from different parts. This is obviously a reference to his body being made of parts from the Andromeda aliens.

Trivia

 * Ultimate Aggregor didn't just "stand there in shock" when Ultimate Kevin attacked him; rather he tried to absorb the attacks but could not due to his inexperience in absorbing that kind of energy.
 * Ultimate Kevin could revert the mutation of Aggregor, and not only 1/10 of his energy, because he used a machine to turn them into pure energy, allowing him to gain the full power of the aliens. This energy is what Ultimate Kevin absorbed.
 * In the game FusionFall, there is a code set that comes with an Ultimate Aggregor Mask.