The Destiny War's final battle begins, and it starts up with a bang. The Avengers, imbued with a bit of the Destiny Force from Rick Jones drive off the Time Keepers, who seem more than anything focused on keeping themselves alive. The trail leads to the lair of the Time Keepers at the end of time where Kang leads the Avengers in an assault on the Forever Cannon, a deadly device powered by the Forever Crystal which Immortus had harvested from the remains of Chronopolis. But as the Avengers press their attack Immortus turns on his masters and denies them the Crystal but they take it anyway and destroy Immortus in the bargain.
To forestall the attacks of the Avengers and Kang the Keepers call forth evil versions of the Avengers from across time and suddenly the hall fills with armies of variations of the great heroes. The Avengers fight on against these dark versions of themselves and press their advantage, led by Rick Jones and the ferocious Kang. Even Libra joins the fray but the proves to be a mistake as the Time Keepers use him to turn the tide and use the Destiny Force inside Rick to freeze the Avengers in their tracks. They then seek to defeat Kang by forcing his transformation into Immortus. Then Captain Marvel, the one member of the team who remembers the war uses the Nega Bands to change places with Rick Jones, as had his father before him. But this Rick is much older and the evidence of many battles is displayed in his clothes and his wounds. He has but one arm, wears Doctor Strange's amulet as a broach, Falcon's boots, and a belt which suggest great utility and a shoulder wrap from a super-looking red and yellow cape, these last two details seemingly of another world entirely. This aged Rick meets and consoles his young counterpart and together the counter the evil Avenger army of the Keepers by calling forth an army of good Avengers from across countless time lines and alternate universes.
The Destiny War rages as an army of good Avengers from across time and space battle an army of evil Avengers. Battles and fights go on in all directions and Avengers on both sides fall. The Avengers led by two Ricks press the attack on the Forever Cannon while Kang fights to forestall his change into Immortus, but Kang's will proves too powerful and he sloughs off their attack. Kang once more he joins the furious fray with savage gusto. Old Rick Jones uses the Nega Bands to again become Captain Marvel to join the fight. The battles rage then young Rick Jones dives into the Forever Cannon and uses his Destiny Force powers to destroy it once and for all but perhaps at the cost of his own life.
He falls and lies still as Kang uses his poweful weapons to seemingly destroy the Time Keepers and with a bold bravado shouts his victory to the stars "Kang Conquers!" Captain America takes possession of the Forever Crystal and despite its allure to alter time he seemingly crushes it denying its power to Kang. The that aspect of Kang which almost became Immortus takes shape as a child who quickly grows into a young and vital Immortus who fired with new purpose leaves the scene and the Avengers behind. Kang now at long last free of his destiny to become the hated Immortus feels empowered and alive as never before and seeks new conquests. He too disappears into time.
To save Rick Jones Captain Marvel bonds with him as his father had once done at the end of the Kree-Skrull War and the two become a new hero who will have adventures following this one in a new title. The Libra steps in and sends them all home, with memories which will seem like dreams. Captain America is returned to the pitiless moment which shattered his confidence as a man dies in the White House, Yellowjacket returns to marry the Wasp, Hawkeye returns and makes a call about a mystery man he's found who we know to be Hercules, Mockingbird returns to the mansion to find Jack of Hearts and Wasp who know well of the Destiny War. Wasp and Giant-Man return to help the Avengers as they have always done. The Supreme Intelligence though gets the last moment when we see that he has taken possession of the Forever Crystal, and it suggests adventures to come, as always.
Kurt Busiek said that Avengers Forever was not the story he and Carlos Pacheco began to tell, that one was too similar to an X-Men begun at the same time. So they switched it up and cobbled together this ultimate Kang epic, at the same time weaving together the myriad threads of nearly all the Avengers lore which had attached itself to Kang over the decades. Like the best jazz, they began with no real clear destination but rather allowed the story to unfold over time and seek its own ending. It did with a bang. Now if the finale of Avengers Forever can be faulted for anything it's that it has so many heroes in attendance that we never get a good look at all of them. That's frustrating, but there's no denying the gusto which permeates ever page of this wild time travel yarn.
Busiek has said he wanted to emulate what Roy Thomas, Neal Adams and the Brothers Buscema accomplished with the historical Kree-Skrull War, make a sprawling epic without a pre-ordained plan, allowing incidents and events to happen which would inform the direction of the story. I don't know the extent to which he and Pacheco accomplished this, but I do know the final result is a story which lingers in the mind like a fine meal.