Think back to the late fall of 2007, if you can. If you were a TV buff at that time, there were a handful of shows that mattered. The Sopranos had just ended its run, while Mad Men had just begun. 30 Rock had come roaring onto the scene over the course of the calendar year, unleashing many of its funniest episodes. And one of the big questions left hanging by the TV season that had ended the previous spring was what, exactly, was up with Lost’s flash-forwards.

Yet the show of the moment, arguably the most buzzed-about program of that point in time, was Dexter, Showtime’s serial-killer thriller, which ripped through a second season that was so critically acclaimed and so successful with viewers that CBS actually aired bowdlerized versions of its episodes in prime time while waiting out the concurrent writers’ strike. The series had been promising in its first season, but in its second season, it dug deep to come up with a riveting story arc in which the many corpses Dexter Morgan had tossed into the ocean from his boat resurfaced and forced him to find a plausible cover story, while Sergeant James Doakes, the one coworker who suspected Dexter of being anything more than the dorky guy from the office, closed in on his prey.

Sure, the season ended poorly, with a finale that let Dexter off the hook for all the difficult moral choices it presented to him, but that was the sort of thing that could easily be fixed in the show’s third season. Dexter had arrived. It was the next great television drama, the show that would put Showtime on the map as real competition for the flailing HBO. Even better, it was anchored by a fantastic, defining performance by Michael C. Hall, who exploded his Six Feet Under persona to play a man with a razor-sharp smile that hid more demons than it ever let out.

It didn’t last. Dexter would never again rise to that level of quality, and the one time it commanded as much critical and audience buzz as it did in its first two years came almost entirely because of guest performer John Lithgow, who was killed off in the finale of the same season he joined the show. After that fourth season, the show staggered on for another four years of increasing irrelevance, and it will wrap its run on Sunday at the end of a season that has been almost completely free of drama or conflict, and which featured (in the penultimate episode of the whole series, no less) the idea that Dexter Morgan, the Bay Harbor Butcher, could learn to stop serial killing if he just fell in love with the right woman. (She, Hannah McKay, played by Yvonne Strahovski, was also a serial killer, who presumably also found her urges sated by true love. One can only imagine the episode set five years in the future when she’s ready to kill again because the thrill is gone, and Hall stares at her with a hangdog expression, like when Nancy and Elliot had to go to couples’ counseling on thirtysomething.)

Dexter did most of this to itself. Its fifth, sixth, and eighth seasons are frequently and stunningly incompetent, and its seventh season wastes a promising beginning in favor of the same old, same old. Yet it’s not hard to look back at the end of that second season and wonder just what went wrong. Now, that disappointing season finale looks like a harbinger of things to come, an early warning sign that nothing on the show would be taken seriously and consequences were unlikely to arise.

Look a little harder at the calendar, though, and it becomes even more apparent that Dexter’s flaws were thrown into sharp relief by another show that debuted a few months after that second season ended. Though greeted with mostly positive reviews, almost nobody watched its strike-abbreviated first season, and its renewal was hardly a sure thing. Yet over the course of its run it would grow into one of the best shows ever to air on television, eventually wrapping up at almost exactly the same time as Dexter. I’m talking, of course, about Breaking Bad, a show that did right almost everything Dexter did wrong.

As I’m writing on the Internet, I likely don’t have to explain to you just why Breaking Bad is having such a successful final run of episodes. You’ve likely seen for yourself. What’s interesting is just how similar the final 12 episodes of Dexter (so far) are to the final eight episodes of Breaking Bad (so far). Or, rather, what’s interesting is that both stories started in fairly similar places — someone had discovered the protagonist’s big secret, and a former partner was on the verge of turning on him — then took incredibly different paths toward their respective series finales. Breaking Bad heightened its conflict endlessly, leaving the quieter domestic drama the show had launched as far behind, in favor of sheer pulp. Dexter did … the opposite of that. (To be sure, it’s been difficult to ascertain exactly what Dexter has been trying to do for some time now.)

The above is cheating a little bit, because the two characters — the one who discovers the secret, and the former partner — on Breaking Bad are legitimately two characters (Hank and Jesse); on Dexter, they’re the same person: Dexter’s adopted sister Deb. Dexter has occasionally forgotten what to do with Deb throughout its run, but her survival has largely been assured since so much of the show’s drama was built around wondering what would happen once she, a homicide detective, discovered that her brother was a murderer. She figured this out at the start of the show’s seventh season, which gave her a leg up of about 16 episodes on Hank, and in some ways, her journey through denial toward acceptance of her brother’s extracurricular activities was more nuanced than Hank’s journey on Breaking Bad. (Vince Gilligan and his writers had basically one episode to convey that journey, both by the very design of the show and by the necessity of AMC’s odd, bifurcated season structure.) Deb covered up Dexter’s activities because she loved him, then came to a kind of queasy peace with it before killing someone to protect him in the seventh season finale. She had, in other words, pulled the full Jesse Pinkman.

Of all the similarities between the programs at this late date — and here’s another one: Both final seasons have frequently revolved around fleets of new characters who are less immediately compelling to regular viewers than the regulars, though only Breaking Bad has had any idea what to do with its guest stars — perhaps the greatest one is contained above. Jesse became the secondary protagonist of Breaking Bad after shooting Gale Boetticher at the behest of Walter White. His journey toward a place where he was ready to give up on the drug trade was agonizing and honest, one of the show’s best emotional arcs, and the series respected that arc by giving him material as rich as Walter received. Dexter never realized that the burden of its story had shifted to Deb, instead treating her as an inconvenient thorn in Dexter’s side.

The worst thing about this is that Dexter had a potentially brilliant final arc — one that would have redeemed many of the show’s sins — set up in the first four episodes of its final season. But it didn’t bother pursuing it because the show eventually became unwilling to view Dexter Morgan as he truly was. In those first four episodes, Deb has quit the police force over her devastation about what happened when she tried to protect Dexter, and she is working as a private detective. She’s drunk and on the edge of despair. Dexter, like the uncaring asshole he can be, keeps trying to force himself back into her life. (Typical of the show at this late date, the series views this as a good thing, mostly.) At a pivotal point, Deb realizes a criminal she’s trying to bring in is probably just better off dead, so she murders him and covers it up (she has experience now). Pushed to the brink, she tries to confess to the earlier murder, but no one will let her, not believing she’s capable of it. Finally, she decides Dexter caused this to happen, so she has to rid the world of him. While driving him around, she jerks the wheel of her car and drives it into a lake, where it sinks beneath the surface.

It’s a dumb cliffhanger — Dexter isn’t going to kill its title character in the first four episodes of its final season — but it could have worked as a sign of Deb’s mental state. The show had two potential paths here to follow: It could have seen what happened when Deb decided to follow in her brother’s footsteps, culminating in Dexter and Deb simultaneously realizing that the other has to be removed from Miami if things are ever going to get better; or it could have had her realize what he’d made her do and come clean to the Miami police, giving all the show’s useless supporting characters something to do. Dexter, finally forced to go on the run, would struggle to stay one step ahead of the person who knew him best. Mix in one of the show’s famed serial-killer villains for Dexter to hunt down, and that might have made for something at least serviceable.

What Dexter handed viewers instead is one of the worst seasons of television from a formerly good show that’s ever existed. At all times, it’s been clear that the show viewers thought they were watching — a dark drama about a serial killer with questionable morality — was very different from the one the writers thought they were creating: a show about whether Dexter can transcend his nasty little habit, like it’s an addiction to cigarettes. The show retrofitted Harry’s Code, the rules for serial killing that Dexter’s adopted father gave him as an attempt to keep his psychopathic tendencies in check, into something a psychotherapist whom Harry had once known came up with. It then spent far too long with a bunch of guest characters it tried to turn into a surrogate family for Dexter. (That psychotherapist was played by Charlotte Rampling, who was so good that it took more episodes than usual to realize the writers had no idea what to do with her.) Deb, instead of turning on her brother or copying his methods or anything, mostly tossed up her hands and said, “Serial killers! Whaddaya gonna do?” It was a colossal mess, dramatically inert even before Dexter was cured by love.

The most telling bit of evidence explaining just why Breaking Bad used so many of the same basic story elements as Dexter and beat it at its own game is that both shows sat down with Sundance’s The Writers’ Room, a behind-the-scenes series about many of TV’s biggest shows, hosted by Jim Rash. The Breaking Bad episode indicates just how smart Gilligan & Co. are about knowing how much they can needle at Walter White’s morality, then pushing him exactly that far so the audience realizes the full weight of everything the man has done. The show works because of its great acting and fantastic plotting, sure, but it’s also successful precisely because it has a very clear view of its main character.

By contrast, the Writers’ Room installment on Dexter indicates just how far gone the show’s writers are. They talk of the arc of the show less in terms of Dexter having to come to terms with what he’s done — or others having to pursue him because of those acts — and more in terms of the character becoming a “real boy.” They describe him in terms reserved for comic book superheroes. Sure, he’s killing people, but he’s only killing bad people, right? That’s not so awful. Maybe Dexter’s just misunderstood.

The problem with this idea is that Dexter itself has contradicted it in the final season. If Dexter can stop killing, if he was just a misdiagnosed sociopath (or whatever) who just needed the love of a good woman all along, then what about all of those people he killed on his table over eight seasons, tossed into the depths in Hefty bags? Couldn’t even one of those people have managed to turn their lives around? It’s as if the show forgot that a vital part of Harry’s Code has always been “Don’t get caught,” the tacit acknowledgement that what Dexter was doing was illegal and immoral, an attempt to do a patch on a malfunctioning bit of human software. In its second season — when it was revealed that Harry killed himself after seeing what he’d made his son — the show was clear-eyed enough to at least approach this idea. In its final season, that was shunted off to the side in favor of tearful good-byes and “I’m gonna miss you, pal” speeches that seem airlifted in from the series finale of M*A*S*H.

Dexter could have been a great show coming out of that second season. Think of how exciting it would be to have two antihero dramas going out at the top of their games right now, then think back to those early episodes of this season of Dexter to realize how close that notion actually came. There is always room for more than one antihero on TV. (Just ask Tony Soprano, who had to deal with a whole fleet of them while he was around.) But seeing the final season of Breaking Bad juxtaposed against the final season of Dexter simply reveals how little teeth the latter show had all along.

Like or hate Breaking Bad (or Walter White), it’s impossible to come away from that show and not think its creative team has complete and total control over what it wants to weigh about its main character. Yet even if you still like Dexter, even if you still cling to hope its finale might right the ship at the last possible moment, it’s difficult to watch this season and not conclude that the character became something else entirely along the course of its run in an attempt to soften him or make him more palatable. Walter White exposes the darkness inside all of us. Dexter Morgan had a chance to do that, but it was pushed aside in favor of more voice-over quips to the audience and reassurances that the guy you’re watching isn’t all that bad, so maybe you aren’t, either. It refuses to challenge either its characters or its audience, and that makes it more of a disappointment than anyone might have imagined back in 2007, when it had the world at its feet.

Todd VanDerWerff is the TV editor of The A.V. Club. His writing also appears in the Los Angeles Times.