The End of Gotham City

Pedestrians on their way to work stepped aside on the sidewalk to avoid Saitama as he shakily walked forward with a thousand yard stare, his hands trembling as he snickered to himself.

"Freak," one businessman muttered as he glanced at the hero's white cape.

Stopping, Saitama considered punching the guy in the mouth, where he began to laugh at imagining the complete destruction of his head against his fist. Looking up, he managed to fight the urge, where he finally took a second the take in his surroundings. It was a busy street that was lined with multiple businesses, with Gotham's towering skyline shadowing the road. Dawn continued to break as the fresh daylight signaled the arrival of many commuters hustling and bustling into the city.

Sighing as he attempted to ground himself back to reality, Saitama's sanity failed to hold and he slipped again into a fit of giggling, where he turned around to find himself standing in front of an appliance store's display window. Still snickering, the bald hero took the juvenile face paint kit that he'd taken from the dollar store and messily began to apply it to his face. Putting a layer of white across all his features, he added some blue around his eyes, and a spot of red on his nose as well as painting a large red smile over his mouth.

"Hehehehe…I've never looked better," Saitama giggled proudly as he threw away the used kit. Random civilians merely looked at him with even more bewilderment, where they nervously shuffled past him on the busy sidewalk. "What? I think everyone should start the day off with a smile!"

"Careful, buddy, you know the Batman has a thing against clowns," a man called from behind a newspaper stand, shaking his head as he resumed counting his register.

"Batman…that's right, he got away," the one punch man muttered to himself, before pounding his head with his fist. "No, no, no, no, that guy was a hero, a good guy. Of course he tried to fight me, I killed his friend or whatever."

Despite desperately fighting with himself to bury his increasingly-dominant sadism and insanity, Saitama couldn't help but be bothered by the fact that one of his opponents had escaped. It had been many years since someone that he'd fought survived their encounter with him, and in his current mental state, that bothered him more than anything.

"I liked him, he didn't have powers but he used his wits…hehehehe," the bald hero chuckled, his voice again trailing into a laugh. "Although I don't know why, but for some reason, I really, really want to defeat him…HAHAHAHAHA, he must give people in this crappy city so much hope HAHAHAH imagine if I just extinguish that from them!"

His mind straining to contain the disturbing thoughts, Saitama suddenly realized a very obvious and easy way that he could best the Batman. His quickly-shrinking sane side was horrified at the thought, but his growing insanity loved it, and it drove him into a fit of laughter so powerful that he had to lean against the store window to stop himself from falling over.

"Yes…that's what I'll do!" Saitama wheezed as he got over his laughing. Bending his knees, he shocked the many passing people as he leapt through the air in a super jump that vaulted him all the way across the city, where the many buildings sped by below the bald hero as he eventually reached the outer suburbs and then finally, the outskirts of the city.

Landing hard on a patch of grass, Saitama turned around to see the city in full view. A "Welcome to Gotham City!" stood off of a nearby highway running into town, where the troubled hero figured that this would be the best spot to pull off his plan. Walking over to the road and turning to face the city, ensuring that as much of it was in his visual range as possible, Saitama rolled back his shoulder and clenched his fist.

"Serious Series: Serious punch!" the caped baldy yelled with a manic smile on his face as he exerted the tiniest bit of effort into this attack compared to the rest of his punches. The effects of the gargantuan blow were felt immediately, as nearby trees were blasted backwards and many were completely uprooted as the barreling shockwave came straight at Gotham city. A second later, Saitama's face froze in a wide, toothy grin as a titanic explosion shook the Earth.

Miles away, the all-powerful punch tore through the city with the force of several nuclear weapons. 90% of Gotham's buildings were obliterated in a matter of seconds, where millions of people didn't even know what hit them as the debris from the structures around them annihilated their flesh and bone. Tens of thousands of vehicles were shredded and compacted into scrap metal as roads and highways collapsed and crumbled into dust before being blown back by the tremendous blast.

The remaining 10% of buildings suffered extensive damage as if they were right next to a category 5 hurricane. People were buried alive in their homes, and anyone unfortunate enough to be outside was blown away as if they were in a wind tunnel, before coming to an abrupt splat against any still-standing structures or debris.

Laughing hysterically as the aftershocks of his punch shook the area around him and caused the clouds to part up to thousands of miles away from the destroyed city, Saitama's sanity emerged for one last time. His clown face contorting into an expression of deep horror, and tears filled the hero's eyes as he realized the extent of the damage that he'd just done.

"T-that city, it looked like millions of people could have lived there," the fallen hero muttered in dismay. "What have I done? What do I- hehehe….HAHAHAHAH, now if that didn't kill the Batman, then I don't know what will! Too bad tall those other people were in the way, but you know what they say: can't make a bat-omelet without cracking a few MILLION eggs! HAHAHAHAH!"

With the notion that he'd just murdered nearly an entire city, what was left of Saitama's once helpful, albeit indifferent personality was buried, and what remained was nothing but an empathy-lacking, diabolical monster. Whatever it was that the Joker had sprayed him with had tainted the hero's mind and turned it into one that was very similar to the villainous clown's. The transformation was complete, creating a new homicidal maniac who had the power to destroy nearly anything with a single punch.