I'm going to do a bit from Flash's view, and from Superman's view too.
This is from my boyfriend's head-cannon, in which he has linked up every game, book, story that he likes together - Ie: Aquaman, in his head-cannon, was the first ruler of Rapture from bioshock, and general DC comics lead into the worlds of Fallout and the Hunger Games.
Batman pulled the welding mask from Joker's head, exposing his bloodied, glee filled face. The vigilante sent a hard punch into the laughing man's face, sending two of his teeth flying across the room, Joker let out a loud, wheezed laugh.
He spat out a mouthful of blood, "You can hit harder than that, Batsy! Why do I get the feeling you're holding back?"
Batman sent his fist into Jokers jaw again, making the clown let out a hiccupped cough of laughter. "You can see it can't you, Batman? Because of what happened to you, you can see, you can see why I do this!"
"No, Joker!" Batman screamed into the white face, "There is no reason for this chaos!"
Joker's face split into a wide smile, and a deep chuckle clawed its way from his lips. "Just one bad day, that's all it takes, and chaos becomes normal! It happened to you, it happened to me… One bad day and the world will go as mad as us."
One last punch silenced Joker, leaving him unconscious.
And Batman escaped again into the night, leaving Gordon to clean up the mess the madman had made.
…
Bruce sat on the sofa, his head in his hands, listening to the news report.
"-in the wake of Joker's death mass riots have occurred in Black-gate and Arkham, the mayor has called in a greater military force to help deal with the threat."
Bruce flicked off the tv. "Hey," Tim whined, "I was watching that."
Bruce's eyes flicked to his feet, "I don't want to listen to it again, I don't need to listen to it again, I was there."
"It wasn't your fault…" Tim offered.
Bruce sighed, "I know, I've gone over it so many times in my head…."
…
"The new president of the united states was sworn in today, Lex Luthor took his first speech as president-" Bruce turned the tv off.
"Father!" Damian frowned, "I was trying to watch that."
"We were there, you know what he said," Bruce growled.
"I find it hard to believe that people voted for him… They should be castrated…" Damian said as he got to his feet, beginning to walk from the room.
"…He was the lesser of two evils. If Superman was here this never would have happened," Bruce said with a hint of disgust to his voice.
Damian nodded, stopping by the door, "I'm sorry, father…"
"I've not given up hope. They've not found a body yet."
Damian nodded, "Yes, but…" he shook his head; there was no point in pushing it, he would never listen.
…
"Superman's body was found on Chinese soil today. Lex Luthor is taking part in peace talks this afternoon."
…
The military influence at the prisons in Gotham had been growing steadily, Batman had noticed. He was beginning to hate catching his rogues, because he knew he'd have to take them there; Riddler and Scarecrow had tried to arrange a breakout about a month ago… Bruce hadn't had the heart to stop them.
He'd seen them coming out, and one of them, he wouldn't mention which, had burst into tears, and screaming that it was too awful in there, that he'd do anything to get out, pleading with the vigilante to just let them go.
He could see their bruises, their cuts, the way Jon was limping… He couldn't take them back in there…
…
"Word has reached us that Chinese forces have mobilised, we are on the edge of war, despite protest President Luthor has declared martial law in the USA to help deal with the imminent threat of spies."
…
Batman heard a gunshot, a few streets away, "…No…" Bruce mumbled to himself.
He ran to the area where he heard the shot, he heard voices, and a woman screaming.
"Please, Miss, go back in your home," someone said.
"You shot him! My baby! You shot him!"
"Miss! Back in your home now or I will use force!"
Batman rounded the corner; two soldiers with guns, a boy, no older than 15 crumpled on the floor, and a woman crouching over him, screaming her head off.
Batman threw a batarang into the nape of one of the shooters necks. The other soldier turned, but couldn't react quick enough, and he too fell to the floor with a gash to his neck.
Batman dropped to the boy's side, checking him over; he'd taken a clean shot through the leg, he was unconscious.
Batman pulled a small medical kit from his belt and began to fix the small wound on the boys leg, "What happened?" he asked the crying woman.
"Th-the cat got out, he ran after her and they shot him!" she said with a sob.
"It's ok," Batman said gently, "He'll be fine. Make sure he rests, take him o the hospital as soon as you can."
She nodded as Batman lifted the boy, taking him into the house. "T-thank you… they would have left him there to die…"
"He'll be fine… Miss. You need to make sure he stays inside after dark…"
…
"Get to the batcave now," Bruce said as calmly as he could, "There's nothing we can do now."
Damian nodded, gathering up his things, Tim and Dick were already down there.
"Damian, come on," Bruce whined, "We've got two minutes until the bombs hit."
"Ok, I'm ready," Damien said, taking his bag and rushing down the stairs.
"We've got everything?" Dick asked, his voice filled with worry.
Bruce nodded as they descended through the caves, to the bunker Bruce had set up.
"We've got enough for years."
"We won't need it, the meta's will be able to disarm them."
Bruce shook his head, "There is no way they'll be able to disarm them all."
…
They could hear the bombs dropping, feel the ground rumbling as they hit the floor.
The world was ending, and there was nothing anyone could have done to stop it.
Bruce frowned to himself… Had Joker known this would happen?
The world was having it's 'bad day'…
It would end human existence as they knew it. Everyone left over would have to fight for survival.
Everyone left would be 'crazy'.