Sentimonster Ladybug

"Thank you, Ladybug. I will help you!"

- Sentimonster Ladybug deciding to assist Ladybug and Cat Noir.

The Sentimonster Ladybug, also called Bugette by Ladybug and Cat Noir, is a minor antagonist in the French-superhero cartoon series Miraculous: Tales of Ladybug and Cat Noir. It is a sentimonster created by Mayura for the purpose of helping her obtain Ladybug and Cat Noir's Miraculouses, although she later turns against her upon gaining sentience.

Like the real Ladybug, she was voiced by Anouck Hautbois in the French dub and by Cristina Vee in the English dub, who also voiced Risky Boots and Rei Hōōmaru in the English dub of Kill La Kill.

History
In "Ladybug", after stealing back the Peacock Miraculous from Gabriel in his sleep, Nathalie travels to the Place des Vosges to buy a Eiffel Tower key chain and then down to the sewers, revealing to Duusu that she plans on creating the most powerful sentimonster to ever exist in order to capture Ladybug and Cat Noir's Miraculouses. She subsequently transforms into Mayura and infects the key chain with an amok, molding her dedication into a sentimonster in the shape of Ladybug. Once the Sentimonster Ladybug is completed, Mayura informs her that she is Cat Noir's true partner and that her goal is to steal the Miraculouses, with her agreeing.

Later, Mayura and Sentimonster Ladybug stage a fight on the Arc de Triomphe, which prompts Adrien to transform into Cat Noir in order to help the latter. When Cat Noir arrives, Mayura orders Sentimonster Ladybug to pretend to be hurt, which draws Cat Noir to her side. Realizing that Cat Noir doesn't suspect anything, Mayura has her pretend to confess her love for him in order to covertly steal his Miraculous, although the real Ladybug arrives and breaks the two up before this can happen. Cat Noir is perplexed by the appearance of two Ladybugs, and Sentimonster Ladybug convinces him that the real Ladybug is actually an akumatized villain, much to the former's annoyance. However, she goes along with the lie and claims that she won't let Cat Noir destroy her earrings, which he and Sentimonster Ladybug prepare to do, only for Mayura to fearfully order him not to, revealing her deception in the process. Sentimonster Ladybug subsequently takes Mayura's side while Ladybug and Cat Noir deduce the former' true nature and that it's amok is hidden in Mayura's key chain.

Mayura then orders her to steal Ladybug and Cat Noir's Miraculouses and to not hold back, causing Sentimonster Ladybug to summon a giant adhesive blaster using her Senti-Charm, while the real Ladybug summons a fork with her Lucky Charm. Sentimonster Ladybug engages Ladybug and Cat Noir, although the former manages to defeat her by using the noise of scraping a glass pane with the fork, distracting Sentimonster Ladybug and Mayura long enough to grab the key chain. However, instead of purifying the amok, Ladybug realizes that her copy is controlled by whoever possesses the key chain and that she couldn't help but follow orders, deciding to give her the key chain instead, asking her if she will help them defeat Mayura. Sentimonster Ladybug agrees to Ladybug's request and helps her and Cat Noir corner Mayura; although, before she can be defeated, she swiftly revokes the former's amok, destroying her in the process. Cat Noir immediately tries to attack Mayura in a rage, only to be fought off by Hawk Moth, who briefly fights with him and Ladybug before rescuing her. Afterwards, Ladybug uses her Miraculous Ladybug to reverse all the damage that had been caused, although she and Cat Noir find that it was unable to restore Sentimonster Ladybug, much to their disappointment.

Trivia

 * Sentimonster Ladybug is the first character in the series to have been both directly and permanently killed off by a villain.
 * Along with the other sentimonsters, and Ladybug and Hawk Moth (in the alternate timeline seen in "Cat Blanc"), Sentimonster Ladybug is one of the few characters in the series to have been visibly killed off in general.
 * She is so far the only sentimonster to have ever turned on Mayura, and, aside from Robustus, the only created villain to have ever turned on her or Hawk Moth (although the former did so in order to seal Ladybug and Cat Noir's Miraculouses for himself, rather than having redemption like Sentimonster Ladybug).
 * She is the third character to be an evil replica of Ladybug, the first being Antibug (Chloé Bourgeois' first akumatized form) and the second being the Nightmare Ladybug created by Sandboy.
 * Unlike them, however, she is the first to not summon a sword as her weapon when using a replica of Ladybug's Lucky Charm.
 * After Feast, she is the second known sentimonster to have full control over herself.
 * Sentimonster Ladybug's line "Cat Noir, I don't feel so good" is a reference to Spider-Man's final words in Avengers: Infinity War.