When the series finale of HBO’s mobster drama “The Sopranos” ended with a sudden cut to black, some fans cried foul. Others cried genius. Either way, it was unforgettable.

This fall the pressure to “end well” is on for a trio of long-running, critically acclaimed dramas — “Boardwalk Empire,” “Parenthood,” and “Sons of Anarchy” — and the showrunners are planning potent final episodes.

“A great ending stays with you. It resonates,’ ” says “Boardwalk” executive producer and one-time “Sopranos” scribe Terence Winter. “It’s something so powerful that you sit with friends and talk about what it might mean, the deeper implications.”

To increase the intensity in the “Boardwalk” series finale, the season premiere jumps ahead seven years to 1931 and finds bootlegger Nucky Thompson (Steve Buscemi) at the start of the Great Depression, where he sees the devastating effects of alcohol on a broken population.

“This year, Nucky witnesses what he has wrought because of his lifestyle,” Winter says of his HBO drama. “I always wanted to explore the effects of what Nucky did for a living. I had an end point for him from the beginning. Now, I know in specific detail how it exactly happens. He sees the chickens come home to roost.”

The specter of remorse also features in Kurt Sutter’s outlaw motorcycle club drama “Sons of Anarchy.” This year, president Jax Teller (Charlie Hunnam) will descend to new depths after the murder of his wife, Tara (Maggie Siff), in last season’s finale.

“After Tara’s death, our hero will be in a darker place,” he says. “The level of violence will be higher; it will feel like a more violent season because of Jax’s emotional state.”

The season will bring resolution to the relationship between Jax and his powerful mother, Gemma (Sutter’s wife, Katey Sagal), who, unbeknownst to him, is Tara’s killer.
If Jax discovers the truth, it could make for a violent finale; but for as often as “Sons” has been compared to “Hamlet,” it’s not going to end like the Shakespeare play. “All the characters are not going to be lying in a bloody heap, drenched in blood and poison,” Sutter promises.

“It’s about being true to the characters, the narrative, and having things unfold in an organic way,” Sutter says. “You don’t write towards something epic or manipulate story to have it feel like a giant ‘a ha!’ It has to end the only way it could have ended.”

A gentler family drama plays out in Jason Katims’ “Parenthood,” the story of three generations of the contemporary middle-class Braverman brood on NBC. The main storyline of the shortened 13-episode season will launch in the premiere and focus on aging patriarch Zeek (Craig T. Nelson). All the characters will get storylines, but Zeek’s arc will affect everyone.

“It’s a season about passing the baton from generation to generation, and the family continuing,” Katims says. “You’re dealing with people moving on and maybe losing people. In the last couple episodes, several big life events will occur. When some of the best things are happening in life, some of the hardest things are happening, too.”

“I feel like we owe the audience an ending where there’s catharsis, and a few unexpected things,” says Katims, who wants to create a series finale mood similar to the one he evoked for the final episode of “Friday Night Lights.” “It was about new beginnings.”

To set up striking send-offs, these showrunners are turning to classic storytelling tools. “Parenthood” will get its own time jump; it comes midseason and takes the action forward a few months.

“Boardwalk” flashes back to Nucky at ages 10 and 20 to flesh out how he became the man he is. “Sons,” as always, lightens the darkness with comic relief, some of it in the form of returning guest star Walton Goggins as transgender escort Venus Van Dam.

All these showrunners say that the process in the writing room is basically the same as it has been every season. It’s the feeling in the air that’s different.
“You don’t have to hold back in your storytelling,” Katims says. “You don’t have to think, ‘Do I want to save something?’ or ‘Is there no story left to tell about that character?’ which you always have to think about when the show is continuing for seasons to come.”

Sutter joked on Twitter that he had to put his cardiologist on speed dial. He says, “It really is the toughest season for me to write. It’s a combination of denial that it’s over and trying to avoid the inevitable.”

Because endings are a kind of death. The showrunners reveal that we can likely expect to mourn some beloved characters as these series wrap up.

“A few actors have actually requested that we kill their characters,” says Winter, who has just finished outlining the series finale. “I can’t say who; I can’t say whether we did. People want to go out with a bang. They’re like, ‘Can you give me a really horrific, bloody death?’ It’s like, yeah, why not? You want to go out in a blaze of glory.”

Or a beam of hope.

“No matter how dark the episodes, you have to have redemption or hope,” Sutter says of his FX drama. “We’re heading in that direction.”