Rojo

Rojo is the leader of a heavily-armed female biker gang who first appeared in The Alliance.

Appearance
In the original series, Rojo had maroon hair, pale skin, and wore a gothic black jacket, grey shirt, brown jeans, black belt, black necklace, and gray gloves. Her alien tech armor is a gray and red bodysuit with a helmet,

In Ultimate Alien, Rojo has darker skin and shoulder-length red hair, which is a brighter red than Gwen's. She now wears a steel red armor with silver spikes.

In Omniverse, Rojo looks almost the same as in Ultimate Alien, but with a new helmet, paler skin, and her shoulder pads have less spikes on them.

Personality
Rojo is greedy, wild, amoral, and not hesitant to attack innocent bystanders just because they annoy her.

Ben 10
When Rojo tried to rob an armored truck, she is thwarted by Four Arms and two of Vilgax's Drones coming after him. The remnants of one of Vilgax's defeated drones merges with Rojo as she investigates it, and she becomes a powerful cyborg. Rojo goes on a short crime spree before being contacted by Vilgax, whom offers to teach her how to use her power should she serve him, and threatens to destroy her should she refuse or fail his task.

Rojo is sent after Ben Tennyson and the Omnitrix Prototype in his possession at the hospital where Max Tennyson is staying, she's foiled by Heatblast's efforts. Later on Rojo rampages down at the local police academy in order to draw Ben out, but is turned back to normal when Upgrade merged with her, took over her body and shorted-out the spare parts, after which Gwen Tennyson knocks her unconscious for attempting a sneak attack on Upgrade.

Rojo returns in Ben 10 vs. the Negative 10, as part of the Negative Ten, with new alien tech and armor; presumably supplied by the Forever Knights. In that episode she is also shown to have a rivalry with Charmcaster over being the "baddest girl" in the group. In the battle, she interferes with Gwen and Charmcaster's duel but gets kicked away by Charmcaster and Gwen's combined spell power. Later she quarrels with other Negative Ten members and later was trapped in the force field where the sub-energy once resided.

Ultimate Alien
Rojo returned in Hit 'Em Where They Live, where she and her gang tried to rob a train. She apparently reformed her biker gang and upgraded them, using blue and yellow versions of her new red high-lighted suit. They were eventually stopped by Rath and the gang.

Omniverse
Rojo returned in Color of Monkey. She is hired by Simian to steal an already illegally obtained Tiffin from Argit's new company Argistix. Shortly after being hired she roughed up a couple of bar patrons and ambushed Argit's truck that was supposed to contain the Tiffin, and instead only got a angry Techagon. Having evaded Ben and Rook, she and Simian make a second attempt to steal the Tiffin, with Simian bringing her the Techagon from earlier to have her tear it open.

While retrieving the Tiffin and rendering Simian unconscious, Rojo tears into the willing Techagon and steals the Tiffin just in time for Ben and Rook to give chase on a Upgraded Tenn-Speed. The chase ends at a Mr. Smoothie in Bellwood, where she is surrounded and arrested by the Plumbers alongside Simian.

In The Most Dangerous Game Show, Rojo is one of many contestants who trying, unwillingly, to win Ben's hand in marriage on Charles Zenith's game show. After losing she was transported to the Null Void.

Powers and Abilities
The upgrade gives her the ability to fly, superhuman speed, metallic claws, and a pair of blasters attached to each shoulder. Vilgax is able to communicate with her through the parts and force her to track down the Omnitrix for him. Enhanced Strength, Retractable Claws, Arm-Mounted Laser Blasters
 * (First) Drone Fusion
 * (Second) Armored Suit

Ben 10

 * The Alliance (first appearance)
 * Ben 10 vs. the Negative 10: Part 1
 * Ben 10 vs. the Negative 10: Part 2

Ben 10: Ultimate Alien

 * Hit 'Em Where They Live (first re-appearance)

Ben 10: Omniverse

 * Color of Monkey (first re-appearance)
 * The Most Dangerous Game Show

Etymology
Rojo is Spanish for red, which explains her red armor. But her villain name is not pronounced in the series using Spanish phonetic rules. In Spanish, the letter J makes the H sound, making Rojo pronounced as "ROE-hoe" in Spanish, not "ROE-joe".

Rojo is a compacted version of Robot Joey.