Mine would be called something like "Batman: breaking point" and it would be about Batman finally being pushed to the point where he'll kill.
First he loses all his money.
Which of course leads to him losing Wayne Manor which means no more bat cave, no batmobile, no batwing, no bat computer.
And as his gadgets break he can't afford to replace them.
He actually has to get a job which means he's always exhausted by the time he goes out at night to fight crime.
The stress and sleep deprivation lead to him making mistakes, both physical and mental, and combined with him not having working gadgets, he's suddenly not anywhere near as formidable as he once was. He's taking more punishment in fights, even losing fights and barely escaping with his life.
Until one night he's beaten to a pulp by joker and his goons. He's stripped of weapons/and armor, lying on the ground, his right arm broken and useless. Joker tosses a gun down in front of him and says there's one bullet inside. And that Batman has to shoot the joker in order to save his loved ones. He pulls back a curtain and behind it we see commissioner Gordon, Alfred, Nightwing, and Damien Wayne, all tied up and helpless. Joker says he's going to kill them one by one until Batman picks up the gun and stops him. And then he backs up that threat:
Bang. Gordon dead.
"Pick up the gun, bats!"
Bang. Alfred dead.
"That one's on you!"
Bang. Nightwing dead.
"Too slow!"
Bang...
Joker falls, bleeding from a chest wound. Damien falls, dead from a head wound.
Batman finally picked up the gun and shot the Joker, just as the joker was pulling the trigger on Damien.
The Joker's goons are about to kill Batman when Joker, with his last breath, orders them not to. Joker dies and they carry his body away. Leaving Batman alive.
Batman once said that the reason he doesn't kill isn't simply because it's wrong, but it's that if he does it once, he knows he won't be able to stop.
From here on, the story is about him not stopping.