This is how it goes:
They stop saying that they're retiring pretty quickly. Instead they say they're taking a break. They all know by now that something - a favor for an old friend, a war, a death, their own guilt - will draw them back. It's addictive, this avenging, and they can never quite break the habit.
Tony says he's out, and means it, but then there are the accords, and the war, and after that he wants out more than ever, but he can't. The choking guilt he refuses to acknowledge won't let him, even if the government would have. Which they wouldn't.
He marries Pepper instead and calls it a honeymoon and then puts the suit back on and gets back to work.
Then there's the Infinity War, and by the end of it he has more issues than sanity, but, hey, Steve's back, so the suit feels a little lighter.
There are new team members and more deaths, but somehow the old hats keep falling back into place like there's some kind of gravity pulling them back in. Personally, he blames Fury.
There's a kid now, and how did that happen? He's not ready, he didn't plan this, but he spends a bit more time tinkering than he does in the suit, and he teaches his son everything he knows, and he does a better job than his father did at least. Not perfect, but better. Maybe the next generation will finally get it right.
But he's not out. He knows he's not out. His hair turns white like his father's and he's still not out, because he has the suit, and that's all he needs, right? Just build a better suit to make up for a body that's seen way too many battles and far too much liquor.
He's got a weak heart and a bad liver, and the both just get worse when he gets the call that Pepper's died in a car crash. Just like his parents, except its not the Winter Soldier's fault this time. It was a drunk driver, and isn't that ironic?
He buries himself in his lab with his toys and builds better and better weapons and shields for his teammates. He has to keep them safe. he has to.
They try to drag him out. Rhodey comes, Steve comes, his son comes, but he just keeps tinkering. F.R.I.D.A.Y. helps him, even if he occasionally messes up and calls her J.A.R.V.I.S.
Speaking of, apparently it's the Vision's turn to come talk to him now, but Tony hasn't even let him into the lab yet. He's too busy.
He's building a new suit when the heart attack comes. He's on the floor, and F.R.I.D.A.Y.'s giving off all kinds of alarms, but he doesn't want her, he wants J.A.R.V.I.S. and Pepper and it hurts -
He thinks he hears J.A.R.V.I.S. but that can't be right.
The Vision had broken through the door, but he'd done it too late.
The press chitter around the funeral, of course, and there are as many camera flashes as there are extravagant flowers. It's a show as big as any Tony Stark ever put on, but there are people who care there too, and that was more than he thought he'd have at some points in his life.
His son stands at the grave after everyone's left and isn't quite sure what to say. He feels a little inadequate, but he doesn't curse his father like Tony did Howard. Instead he goes home to a gleaming tower and buries himself in a lab for a week and comes out with inventions that send Stark Industries' stock soaring and a suit to rival his father's.
This is how it goes:
They wonder who's going to be next, of course, because this feels like the beginning of the end. They have died before and left before, but never like this. Never with such a sense of finality, never with no one to hunt down and blame.
Natasha has aged gracefully. She is still beautiful and still deadly, even if she moves a little slower now, even if her cover is burdened by so much history that sometimes old scars shine through before she can hide them.
That might be why they catch her. No one is ever quite sure.
It isn't a mission with the Avengers. She's working under S.H.I.E.L.D. directly at the moment. Hill's director and doesn't appear to currently be evil, and this mission at least doesn't have either the scent of corruption or end of the world stakes attached to it.
That might be why they catch her. She might have let her guard down.
She goes in, and she's beautiful and deadly, but what happens, what really happens, is that her Widow's Bite fails her. It glitches, it breaks, because its only been six months since Tony died, and they're only one month overdue for maintenance, and she's sentimental about her weapons even if she doesn't show it. She can't quite bear to hand them over to someone else to repair, not yet. She will after this mission.
Her Widow's Bite fails her, so she uses her hands. Her enemies go down, but one gets her in the leg. She runs for the extraction point, but she's slow. The injury hurts, and so does the one she got in the Infinity War, right above the knee.
She's slow. They're not.
She's on a bridge and she jumps, trusting someone, Falcon or Thor or Clint in a Quinjet to catch her. Her guns are firing as she falls backwards, and she takes out two more.
Return fire catches her in the heart before she hits the water, and that's good, because she never realizes that the backup she was counting on wasn't there.
She hits the water.
The men are caught not twenty minutes later. Director Hill has the river dragged over Clint's objections. He doesn't see the point; Nat won't be there, she'll be turning up wet but never bedraggled in a little bit, and she'll tease them all for forgetting she's got more lives than a cat.
They find the body. Clint doesn't want to go identify it because it won't be her, and he's got other things to do, like interrogate the men so they can figure out how Nat got away. If she isn't back by now, then she must be hurt, and they need to find her so they can help.
Steve does it instead. The bullets hit her chest, not her face, and the DNA matches up. He checks for the scar that for some reason she never got patched up, and he goes to tell Clint.
They hold a funeral. Clint doesn't want to go, but finally concedes because it would suit her sense of drama perfectly to turn up in the middle or to haunt the grave after.
It's the third time he's buried her, and he refuses to believe that it will be the last.
This is how it goes:
They're worried at how fast it's all falling apart, but it's years before they gather at a grave again.
It's a triple grave this time, Sam, Rhodey, and the Vision. Wanda's lost control, and they have to go after her. Nothing ever hurts quite so much as hunting one of their own.
They take her down, but they've lost Scott too by the end of it. His daughter takes up the suit over just about everyone's objections.
The game hasn't been fun for a long, long time, but they're still addicted, and they keep coming back. Is it any surprise they've gotten their children hooked too?
This is how it goes:
They go a few more years without serious incident. The younger ones smooth out their rough edges, and they find a balance again.
Clint isn't out. He hasn't retired. He's just old, and human, and spending more time on his farm with his grandchildren then he is in the Quinjet he uses to stay in the game.
He still hasn't given up on Natasha.
It's Christmas, and they all know what that means, so he's eating with his family while he can, and he's got his phone out for when it inevitably rings.
It's the doorbell instead, and it's an old enemy that's come to call.
Clint isn't out of the game. He's not decrepit, he's not useless, and he's certainly not unarmed, thank you very much. It's Christmas; he's got more weapons on him than teeth.
His family is used to the idea that they could come under attack, and they're ready.
Just not ready enough.
Someone gets off a call on Clint's phone.
The Avengers burst in, weapons drawn, and follow the destruction upstairs. There's a barricade that's been broken down, and an awful lot of blood, and Clint's daughter, holding a gun.
She levels it at them for a long moment, and then she drops it.
Clint had two sons and a daughter, a wife, two daughters-in-law, a son-in-law, and eight grandchildren.
Clint is survived by his daughter.
She joins S.H.I.E.L.D.
This is how it goes:
They look at each other now. They wonder the same things.
Then they don't have to anymore.
Bruce is the Hulk, and the Hulk is Bruce, and both have way too much radiation in their systems. For once hulking out only makes the damage worse.
It's painful to watch him curl in on himself in agony after each battle. It's painful to watch him shrink in on himself in a hospital bed.
The doctors try a cocktail of just about everything, but Dr. Banner seems almost relieved when they move him to hospice.
This, the Hulk can't just spit back out.
It's a long, slow death, and it hurts in ways the others haven't, but it's a quiet doctor they lay into the ground, not a hulking expression of rage, and that's something, they suppose.
This is how it goes:
Steve looks at Thor at the funeral. Thor looks at Steve.
They've both got a pretty good idea who's going to be the last of the original Avengers, but that's all right. They've known that all along.
It's Betty Ross's funeral, and none of them knew her all that well, but it seemed like they should come. Bucky's there too, and he's got a grip on Steve's shoulders like he's trying to ground him there.
They fight and bleed and do what they've always done for eight more months, and then they're in another graveyard, a smaller one, and Darcy's going into the ground. Steve notices for the first time that Jane looks old.
Steve looks at Thor, and Thor looks at Steve, and Steve wonders for the first time if he was wrong.
Darcy is buried with her husband Ian, and they're both near Dr. Selvig.
Steve grips Bucky's arm and wonders what they're going to do when Jane joins them.
This is how it goes:
Thor is not stupid. He knew this was coming. For all the magic he has bargained for and all the time he has stolen, it comes.
Jane is not buried on Midgard. Thor takes her to be buried with his people instead, as suits a princess of Asgard.
Ragnarok is coming, he can smell it on the air. He takes his leave of his brothers in arms.
He does not say he will not return. If he said it was the end, he would be proved wrong, he knows. They are ever drawn back, like moths to a flame.
He might return. But he smells Ragnarok on the air, and they say his brother has escaped, and he thinks the Fates might mean to snip his thread.
He does not say goodbye. He only says it might be a while before they meet again, and they all hear what he does not say.
This is how it goes:
Steve does not look old. He looks older than he did coming out of the ice, but he doesn't look old.
He feels ancient.
Bucky is there, and that's good, and that's terrifying, because he's not sure what he'll do if that changes.
There are new Avengers, new heroes, and he trains them and fights for them and leads them, and most of them adore him, but he'd be lying if he said he didn't sometimes forget their names.
They die and come back, they leave and come back, and he knows it's in their blood, but he also knows they're wrong when they think they're immortal.
Sometimes you don't come back.
There is a battle with some aliens, he doesn't care what they're called, and someone wants to nuke the city to get rid of them.
Well, not nuke. It's something else, but he stopped even trying to listen to technical explanations when Tony died.
They want to destroy the city, and he can't be having that.
He realizes, a little distantly, that they're in New York again. There's a hole in the sky, and he's wearing some strange new suit they've concocted that lets him fly, and there's a nuke, and does this ring a bell with anyone else?
No. It doesn't. Everyone who remembers that battle is dead, except for him.
Bucky stands at a grave.
Everyone who remembers the battle of New York is dead.
This is how it goes:
Sergeant James Buchanan Barnes walks away from the Avengers. He comes back for one last battle, because that's what you do, isn't it? It gets in your blood.
He tells whoever it is in the big metal suit that he wants to be buried beside Steve and then he roars into battle.
This is how it ends.