The title doesn't simply refer to Lila. Adrien is every inch as deceptive as the Con Artist, constantly and consistently lying to his friends, his fellow "heroes" and to himself. He only tells the truth when he thinks it will benefit him, and not a second sooner. And all of this catches up to him over the course of the story, with the added whammy of Lila pulling a Karma Houdini due to her recognizing when it was time to cut and run.
Donating to Lila's Fake Charity drive causes karma to hit the class in another way. Marinette's friends treat the clothes she made for them as though they're worth nothing, with Adrien declaring that she can easily make more, underscoring how they're taking her generosity for granted. Lila subsequently dumps it all at secondhand stores. This means none of them are able to take advantage of Marinette's sudden rise to fame after she's revealed as Ladybug, becoming a household name. This meteoric rise would transform all of her early work into collector's pieces, which wealthy Ladybug fans or rich fashion enthusiasts would happily snap up... if only they had the chance. But since her friends gave them all away in hopes of impressing a stranger whom Lila didn't even know...
When Adrien insists that his classmates aren't giving up anything to Lila that they can't afford to lose, he's not just referring to material goods. He's also emphasizing just how little Marinette matters to him. He's perfectly aware that she's being socially isolated thanks to Lila painting her as a Bitch in Sheep's Clothing, and that it's been taking its toll... but he doesn't care. At best, he expects everyone to be Easily Forgiven for their treatment of her; at worst, he's implying that her friendship isn't worth anything. They can afford to treat their "Everyday Ladybug" like trash, because it's not like she's irreplacable, right?
He's also implictly Blaming The Victims; left unspoken is the suggestion that if they are risking anything of value, then that's on their heads for not being savvy enough to avoid a potentially poor investment.
Adrien's testimony to the police manages to make him look villainous in multiple ways, though the second isn't directly addressed. The first and most obvious is that reporting Lila's crime after months of "dating" her, immediately after his father is arrested, looks like a Frame-Up to cover his own illegal attempt to hide assets from the law. The second is that, since Lila testified in his "defense" just days earlier, playing the Unwitting Pawn who "unknowingly" gave the police information that made it sound like he was working with his father, Adrien's testimony looks like he's trying for a one-two punch of framing her for the emergency funds disappearing and discrediting her testimony. While Adrien's actually extremely naive, Who Would Be Stupid Enough? means it's chillingly easy to read this as Adrien making calculated, if flawed, attacks on perhaps the only witness who can connect him with his father's crimes—it's no wonder the police's view of him is implied to change so much over this interview.
A key aspect of Adrien's downfall is his refusal to act. Not just in regards to Lila; Adrien repeatedly insists that he doesn't need to do anything in order for things to work out. He attributes this to being a "hero" and thus always morally correct, but in reality, this speaks to his entitlement as well as how Gabriel has raised him: Adrien hasn't needed to resolve many matters by himself, as his father typically does so for him.
This also allows Chloé to serve as a narrative Foil to him in another fashion. Both are Spoiled Brats who are used to having their fathers handle things for them — Chloé badgers her father into doing so and throws fits to get her way, while Adrien plays The Charmer and is a Bitch in Sheep's Clothing. But Chloé goes through Character Development over the course of the story, putting real effort into changing her ways, while Adrien repeatedly insists that he doesn't need to act because he hasn't done anything wrong!
This also makes Lila a Foil to both of the above characters; like Adrien, she has no intention of changing her ways and continues to rely on the same tactics that have worked for her in the past (in her case, lying and manipulating people). However, like Chloé, she's able to recognize when blindly doing as she's always done is no longer an option. Instead, she actively changes her goals, cutting her losses in order to focus on more pressing issues, which ultimately allows her to escape karmic backlash and gain an unexpected windfall in the process. Like Adrien, she refuses to change and undergo Character Development, but like Chloé, she takes action when it matters and comes out better off for it.
Overall, action and inaction is a major theme of the fic. As a whole, those who recognize that they need to change and actively work to improve their circumstances wind up earning a Karmic Jackpot. Those who refuse to act, either insisting that they have no reason to do so or expecting others to fix their problems without having to put in any work themselves, are hit by Laser-Guided Karma and will implicitly continue to do so until they finally take the initiative to solve their own problems. Rose is the best example of this, as she initially sides with the class and suffers for it, but her fortunes improve after Juleka coaxes her to a Jerkass Realization and she begins making active efforts to reconcile with Marinette rather than simply expecting to be forgiven.
Trying to convince the police of Lila's guilt after she robs him is, in reality, the worst thing Adrien could possibly do. By failing to stop or report her misdeeds and actively vouching for her honesty to the class while aware that she's scamming them, he's made himself an accomplice to her crimes. Had the police believed him, he would have been open to prosecution alongside Lila. If he was convicted, he could be punished as though he committed the crimes himself, and what money he had left would likely be taken to compensate her victims, leaving him with the additional problems of a criminal record and no modeling money to try and rebuild his life with after turning 18. In a way, Adrien is lucky the police didn't believe him.
Word of God holds that the reason why Adrien suffers such an extreme karmic backlash is that, under normal circumstances, that fate would have befallen either Lila or Marinette, depending on who ultimately emerged victorious. Had Marinette won — something which Adrien prevented — Lila would have been fully exposed as a liar, forced to pay back everyone she'd scammed, lost all her friends and followers, and been sent off to boarding school. But if Lila won, Marinette would have suffered the same fate Adrien does: falsely accused, Hated by All, having lost her Miraculous to Hawkmoth and regarded as a Failure Hero. The possibility of this happening is discussed early on, with Marinette making clear to Tikki that she's on the verge of the Despair Event Horizon; if not for her consulting Luka and finding allies she could trust, Hawkmoth and Lila would have won. Marinette's Karmic Jackpot doesn't just punish Adrien with Lila's karma, it specifically makes him endure what she would have gone through had Lila succeeded. A fate that was very narrowly avoided. Just let that sink in.
Adrien's final fate. His Aunt Amelie places him under house arrest, making clear she's only going to do the bare minimum to support him simply to keep her own reputation intact. This means he's eventually going to have to reintegrate into society once he turns 18, and nobody is making any effort to rehabilitate the toxic mindset that led to all the awful decisions he's made. Adrien will almost certainly be left to his own devices with no understanding of how he went wrong and the public reputation of a willing accomplice to a supervillain who only got away with it through sheer luck, meaning the only logical fate for him is self-destruction.
Check out Karma Overbalance, it pretty much takes Adrien's circumstances to its logical conclusion.
The Karma system has shown to allow someone to get off the hook for everything they've done, including high felonies and federal crimes, as long as they can find someone who will be unlikely to call them out to act as their scapegoat. Karma gave Lila an easy out through Adrien by using the fact that his father was Hawkmoth to make all of humanity want to tear him apart and allowed her to also steal 50M euros from his trust fund. This means that Karma rewarded her for pulling off her cons so well. How many other times has this happened? How many other people were able to get away with all their crimes and bad deeds just because they found someone who (sometimes accidentally) was an easy fall guy just because they failed to call them out for their behavior or even notice it in the first place in time before Karma decides to collect their dues? How many guardians or Miraculous holders were able to do this in the past? And finally, had anyone, especially Lila, found out how Karma's debt system works and took advantage of it?
Lila got away with millions of euros, possibly gained new insight on how to get away with her crimes, knows who Ladybug, the Miraculous guardian, is (as well as the fact that she hated both her and Marinette a lot before she even found out that they were the same person) and the only thing meant to keep her from continuing her cons and bullying tactics is a threat on her life that could potentially be fabricated given to her by the very person she despises. She's also obviously a worse person than Gabriel could ever be. Even ignoring how she was able to steal the Butterfly Miraculous in canon, she's still clearly able to do some pretty impressive and horrifying things when she wants to. Lila now has all the tools and possibly all the experience necessary to succeed where Gabriel failed and steal not only her Miraculous, but potentially all the others as well, including those that belong to her new Miraculous heroes. And if she ever finds out about the Ultimate Power, Adrien would have suffered through all the punishment of accidentally helping Lila and Gabriel (nearly in Gabriel's place) succeed for nothing, since she'll make herself the ruler over everything with that wish and crush Marinette's happy ending under her heel all over again, which is the whole reason he was forced to rot away inside Marinette's old room to begin with. At the very least, considering how awful everyone is in this version of Paris, including the civilians, Karma will definitely get its debt just as thoroughly as it did to Adrien and the rest of Marinette's class.
