IT IS ACCOMPLISHED.

Heroes will live. Heroes will die. The Marvel Cinematic Universe will never be the same after "Avengers: Endgame," in theaters this week.

Back in 2008, the success of the movie “Iron Man” was in no way guaranteed. Starring a battered but still skilled Robert Downey Jr. as the titular hero, aka genius/inventor/drunk/wiseacre Tony Stark, and directed by Jon Favreau, best known for the '90s indie “Swingers,” “Iron Man” wasn’t about a household name such as Spider-Man or Batman. In comics, Iron Man was at his top-dollar best a talented B-lister of a character with a few good stories under his belt.

How far we’ve come.

Over the next 11 years, the Marvel Cinematic Universe became the signature blockbuster franchise of our weird epoch, generating billions of dollars for Disney/Marvel and introducing the non-superhero-comics-reading planet to underknown-yet-awesome characters such as, say, Hawkeye, Black Panther and an ambulatory tree called Groot, among many, many others.

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And now our watch is ended, sort of.

The 22-movie plot arc begun back with “Iron Man” draws to a close with “Avengers: Endgame,” a three-hour, no-kidding epic that manages to jerk genuine tears and generate belly laughs, reference everything from “The Leftovers” to “Lord of the Rings” and stick the landing in a manner comic-booky, extremely fan-servicey and yes, awfully super-heroic.

Let’s see if we can do this with a minimum of spoilers. Much (but not all) of the footage the public has seen in the ads for the film comes from the movie’s first hour. When the film starts, dozens of heroes perished three weeks ago at the end of “Avengers: Infinity War,” after the mad demigod Thanos got control of all six Infinity Stones and rewrote reality, halving the population of the universe. On Earth, the streets are 50% quieter. Trash piles up. The Mets disband. A quiet, lumbering despair reigns.

The heroic remainder — including Iron Man, Captain America (Chris Evans), Black Widow (Scarlett Johannson), Hulk (Mark Ruffalo), Thor (Chris Hemsworth), Captain Marvel (Brie Larson), Nebula (Karen Gillan), Rocket (voiced by Bradley Cooper) and Hawkeye (Jeremy Renner) — struggle to right this wrong. (Many of those folks also happen to be the ones whose contractual obligation to Marvel and Disney is coming to an end.) They decide to take the fight to Thanos. And it sort of ... doesn’t work.

Time passes. One character becomes something of a therapist. One decides to keep running the Avengers. One retires with his wife and child. One becomes the low-key celebrity he didn’t know he wanted to be. One becomes a murderous vigilante. One heads for the stars. One becomes a drunk.

And then a funny thing happens: Scott Lang (Paul Rudd), aka Ant-Man, returns from the Quantum Realm, which turns out to be a great place to hide during a universe-wide genocide. After being told why everyone is gone, he proposes a solution, which he describes as a “time-caper.”

Which is both a good place to stop and a good place to note what directors Joe and Anthony Russo, working with a script from Christopher Markus and Stephen McFeely, have accomplished. “Endgame” moves with the pace and deftness of an old-school, well-executed event comic, the kind of six-issue affair that would eat up a whole summer. Even at three hours, the drag is surprisingly minimal, mostly because there are so many folks to check in on and genres to reference. There’s space opera for the Guardians of the Galaxy and techno-heroics for Iron Man and Hulk (yes, Hulk). There’s rain-slick savagery for Hawkeye and a dicey relationship with responsibility for Thor.

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And then there’s Captain America, the man out of time, the man on whose moral authority the others rely, struggling with the American optimism that Evans seems to embody without breaking a sweat.

It is his story in this movie, perhaps, that elicits the most fist-pumps, cheers and quiet sniffles. Not to mention paying off something that never made sense to me in past movies. When the moment comes — and you cannot miss it, for the audience will be going bonkers — I ... may have yelled “(Redacted) yeah!” in a roomful of stoic critics.

Speaking of Evans, most of those original Avengers know that this is their time to shine, and everyone — from an anchoring Downey to a vibrant Johansson to a hilarious Hemsworth to a very CGI-ed Ruffalo to a surprisingly present Renner — brings their A-game. And everyone (and I do mean everyone) who has ever had an emotionally significant role in an MCU movie makes at least a cameo in this thing.

Which is to say, if you think you need to see “Avengers: Endgame,” you absolutely, positively need to see “Avengers: Endgame."