Nightra

Nightra (spelled Nitra in closed captions, Chicane in TV guide summaries) is a former cadet at the Autobots' training academy, where she was a classmate of Strongarm. She's a former Autobot turned rogue for her own selfish needs and desires.

History
Nightra and Strongarm were best-friends and cadets at the Kaon Police Academy where on one occasion, they were caught by Dropforge drag-racing in the Hall of Studies. On another occasion, they attempted to arrest a Wrecker for speeding, resulting in him damaging Nightra's Autobot insignia and identity signal. After Nightra was caught with a keyfile for one of their exams, she tried to get Strongarm to take the blame, but Strongarm refused to lie under questioning by the Academy's Proctors, resulting in Nightra's expulsion.

After this, Nightra turned to a life of crime until she found herself being pursued by the bounty hunter Blastwave. Stealing his Light Bender and bounty hunter ID badge, she fled to Earth.

Nightra entered the Autobots' base through their GroundBridge, using the Light Bender to make herself appear invisible. After revealing herself to Strongarm and her team, she was invited onto the morning patrol after scanning Strongarm's alt-mode. She used the ID badge to pass herself off as a bounty hunter, and claimed that Blastwave was one of her bounties who had escaped and was now looking for her. The Autobots agreed to protect her, but it didn't take long for Blastwave to appear, causing Nightra to flee. Catching up with her, the Autobots attempted to take her somewhere private, but Blastwave appeared once again and grabbed Nightra, disappearing through a portal to his ship. After Strongarm and her team made it onto the ship as well, Nightra fled to the bridge with Strongarm following. After noticing her sealing off the cargo bay and preparing to jettison it, Strongarm realised what Nightra really was, but she took the control chip to disable the console and used the Light Bender's decoy function to throw Strongarm off. However, Strongarm managed to shoot out the bridge lights to make Nightra's illusions disappear, allowing her to slap stasis cuffs on her and hand her to Blastwave.

Trivia

 * The synopsis for "Guilty as Charged" released through TV listings services referred to Nightra as Chicane, presumably an early working name for the character. While usually referring to an artificial S-curve in a road or racing circuit, "chicane" derives from the same French root as "chicanery", chicaner, which can be translated as "to prevent justice" which may have been considered a bit too on-the-nose, given Nightra's character.
 * Nightra's character model is an altered version of Strongarm's.
 * She has the distinction of being the first rogue Autobot antagonist in an Aligned cartoon (if one doesn't count Roughedge, one of Starscream's bounty hunters).