Chloé and Lila serve as Mirror Characters to each other: Both girls are self-absorbedAttention Whores who focused on making Marinette's life miserable for the high crime of standing up to them.
Both overestimate their skills and are played as Unwitting Pawns by Gabriel. Their willingness to work with Hawk Moth is also what shreds their Karma Houdini Warranties, as solid evidence of their compliance ensures their downfall.
Adrien and Alya reflect each other in many ways as well, starting with their Skewed Priorities: Adrien cares more about his personal comfort and his desire to date Ladybug while Alya focuses on her Ladyblog. Both take these interests to selfish extents, blinding themselves to other concerns.
Both take the status quo for granted, as evidenced by their strained relationships with Marinette. While Adrien stood by and let Lila spread her lies, Alya similarly ignored Marinette's concerns — though unlike Adrien, she wasn't aware of Lila's true nature. Yet once Marinette's Secret Identity is revealed, both believe that they've remained close to her despite their neglect.
Both act entitled to Marinette upon learning that she's Ladybug. Alya complains about being Locked Out of the Loop and declares that Marinette 'owes her' for not spilling her secrets sooner, demanding exclusive interviews and other favors. Adrien, meanwhile, assumes that Marinette being unmasked means he'll finally get the Relationship Upgrade he's been pestering her for.
Despite seeing firsthand how much being exposed has clearly unsettled and upset Marinette, Adrien and Alya both want to willingly expose their own secret identities. This connects back to their respective Skewed Priorities: Adrien thinks that revealing himself as Chat Noir will cause Marinette to fall into his arms, while Alya wants to reveal herself and Nino on the Ladyblog in order to boost views.
Both treat Luka as an 'obvious' Romantic Runner-Up, expecting Marinette to dump her boyfriend in favor of Adrien. Alya thinks nothing of openly dismissing Luka as 'nothing special', while Adrien simply shunts him into the same mental category as Kagami: a clear secondary choice that could never compare to his supposed 'soulmate'.
One critical difference is where Alya draws the line: unlike Adrien, she actually recognizes the impact of Hawk Moth's long reign of terror. Not only was she akumatized herself, so were most of her family — and in several cases, she either got attacked by them or had to fight them personally as Rena Rouge. Adrien, meanwhile, was fighting his father all along without realizing it... but upon learning this, argues that he should be shown leniency for his crimes.
Adrien similarly believes that Chloé and Lila should be Easily Forgiven for their misbehavior, downplaying and dismissing the impact of their crimes. Alya, by contrast, is perfectly fine with their Karma Houdini Warranties running out, and is shocked to learn he doesn't feel the same way.
By the time that the Final Battle arrives, Adrien's Trauma Conga Line has progressed to the point that it's broken through his self-denial. Alya, by contrast, remains stymied by her Skewed Priorities, even complaining to her parents that she's got to film what's happening for the Ladyblog. As a result, Alya sees herself replaced by another Fox and plays no role in the fight, while Adrien's mental breakthroughs help him contribute as Shockwave, and subsequently part with Marinette on better terms.
Agreste and Graham de Vanily families:
Gabriel and Emilie are shown to be Control Freaks who regard their son as little more than an extension of their will, pooh-poohing his desire for freedom as a passing phase. Amelie is far more permissive with her own son, only sighing and lightly admonishing him for rubbing salt in his cousin's wounds.
Gabriel and Emilie disregard Adrien as largely useless, little more than an Unwitting Pawn in their schemes. Amelie genuinely cares for her nephew; while disappointed by his poor judgment, she's concerned about how this will impact his future and wants to help him through his hardships.
Adrien's parents treat his issues as a sign that he's simply incapable of taking care of himself and making good decisions. Amelie treats it more like a problem stemming from his being raised poorly — as in 'he doesn't know any better because his parents didn't teach him well'.
Felix, much like Adrien, shows a distinct Lack of Empathy for others. He is far more open in his disregard, mocking Adrien's misery while pointing out how his own actions contributed to his problems.
Adrien kept quiet about Lila because he didn't want to deal with any unpleasant reactions to the truth. Felix, on the other hand, has no problem with spelling things out plainly, and isn't bothered by how much his words sting.
Ironically, Felix shows more acknowledgement of the notion that Adrien's classmates are more than just 'his friends' than Adrien himself does, by calling out how Adrien's betrayal hurt them so badly that they may not want to be friends anymore, a concept his cousin ignores.
When faced with an illusionary dragon, Felix's first instinct is to stand and fight, trying to defend his mother and cousin. Adrien's first instinct is to run away before remembering that he can't transform into Chat Noir anymore, leaving him feeling completely helpless.
Emilie and Gabriel express their admiration for Felix's intelligence, declaring him to be more impressively capable than their own son. Being self-centered, they attribute this to their own influence and his being a Sentimonster, scheming to take advantage of him by forcibly merging him with Adrien.
Despite his cruelty taking a similar tack to the Agrestes' distinctive Lack of Empathy, Felix ultimately illustrates how far removed he is from them by apologizing to Adrien and admitting his mistakes and explaining himself. This proves to be a turning point for Adrien as well, helping him break away from his own toxic mentality in time to become Hawkbug's Champion.
Alya and Bill 'Buster' Brockman:
Brockman effectively represents what Alya could become: a self-absorbedPaparazzi obsessed with making the world see things their way.
Much like Alya, Brockman fancies himself to be an Intrepid Reporter who ferrets out and reveals the truth for all to see. However, Brockman is secretly Driven by Envy; he resents celebrities and heroes like Marinette for being more famous and respected than he is, and aims to drag them down and destroy their reputations while seeking fame and glory for exposing their secrets.
Marlena turns out to be dramatically different from her daughter; unlike the aspiring journalist, she takes the time to do her research and gather information. She also asks for and respects Marinette's perspective, and is disappointed to learn Alya has not done the same. She also doesn't seek to exploit Marinette's status as Ladybug, whereas Alya expects special treatment and perks for being her 'bestie'.
Marlena, like Tom and Sabine, learns that her daughter was a superheroine. In her case, however, the pride she feels is tempered by several painful realizations about what else Alya has been getting up to that she wasn't aware of, leaving her more disappointed overall.
