The Protagonist's Sister Is Actually The Strongest

In that very moment, the Heavenly Demon showed the King of all Evil the true strength of “mere mortals.” Beings born with no special bloodlines, no unique powers, nothing but themselves and the world around them.

He clenched his fists and unleashed the power he had been holding back this entire time. Every blow he had landed was meant to build toward this single devastating moment.

All those attacks that had seemed insufficient until now had been preparation for this.

The full accumulation of every cursed stigma imprinted into each wound erupted at once. It was a curse so powerful and so pure that not even the King of all Evil could detect or cancel it.

“{Cursed Fist Explosion: Release}!”

“Ngh?!”

Before the Demon could utter another word, his entire body began to inflate. Every punch and strike the Heavenly Demon had delivered now activated the curses imprinted deep within the wounds. Those curses rapidly overflowed with light, transforming into glowing runes that spread across his body.

“W-Wait a second, this is…?! AGH!”

As the power was released, the curses exploded into searing flames injected directly into the Demon’s damned body. It was a technique so potent that not even the King of all Evil could stop it.

“Are you fucking kidding me?!”

BOOM! BOOM! BOOM! BOOM! BOOM! BOOM!

“UUUAAAGGH…!”

The King of all Evil screamed in agony as his body bulged and bubbled. Each internal explosion tore apart flesh, muscle, and bone, sending bloody chunks flying in every direction.

“Were you underestimating me, you fucking bastard?! Taste the power of the strongest Bestia!!!”

With a furious roar, the Heavenly Demon charged forward while his enemy’s body continued exploding. He swung his fists relentlessly and even used his wings as extra limbs to strike, fighting with savage ferocity.

“I’m going all-out! I cannot let this bastard catch a break! I’ll overcome this! For Anna, for my love, for my son!”

His mind burned with a single purpose: to destroy the monster before him. The Heavenly Demon merged all his techniques and martial arts into one. The Spectral Guardian emerged from his soul and aura, moving perfectly in sync with him.

“{Abyssal Cursed Demonic Seal Release}: {Dantian-Destroying Spear Finger}!”

Using the claws on his wings and the fingers he had left, he pierced the King of all Evil’s body repeatedly, punching tiny holes through muscle, skin, and bone.

CLASH! CLASH! CLASH! CLASH! CLASH!

“GRAAAAGGH?!”

As the Demon roared in agony and vomited blood, his insides still exploding, the Heavenly Demon saw the monster’s aura rapidly transform into a massive crimson fist of demonic flames swinging down at him.

CLAAASH!

“Y-YOU LITTLE BIRD…! HAHAHA! THAT FREAKING HURT!”

The King of all Evil laughed maniacally, grinning through the pain. His body was riddled with deep wounds, one arm was completely missing, and he bled profusely from countless gashes.

Yet he still possessed the strength and fury to counterattack.

“Then this will hurt even more!”

The Heavenly Demon roared and thrust his arms forward. His aura surged around them as every ounce of power from his cursed seals and the white void he had gained through regret converged into a single devastating strike.

“{Abyssal Cursed Demonic Seal Release}: {Soul-Shattering Cursed Black Tiger’s Fangs}!”

His aura exploded outward, manifesting as a colossal black tiger that roared with primal fury. The beast tore straight through the Demon’s defensive aura, shattered the arm raised to block him, and sank its fangs deep into the Demon’s scales and flesh, ripping viciously.

“BASTARD!”

The King of all Evil grew desperate. He roared and kicked the Heavenly Demon squarely in the head. The brutal impact crushed his left eye, exploding it into a bloody mess. The Demon’s sharp claws nearly reached his brain.

BOOOM!

An excruciating spike of pain tore through the Heavenly Demon’s skull. He had never endured such agony before, yet that very pain fueled him with even greater strength. He opened his beak wide and bit down hard on the Demon’s leg, tearing it clean from his body.

The King of all Evil screamed in pure torment.

The Heavenly Demon seized the severed leg and incinerated it to ashes with his black flames. The power he absorbed from the Demon’s flesh erupted into a massive surge of energy.

With blood still pouring from his empty eye socket, the Heavenly Demon pressed forward relentlessly. He kicked the Demon’s face with savage force, then drove toward his stomach. His aura fused his fingers into razor-sharp blades as he stabbed dozens of times in rapid succession, targeting the intestines and ribs.

“{Abyssal Cursed Demonic Seal Release}: {Dismembering Abyssal Rhinoceros’ Horns}!”

His aura erupted into a massive, monstrous rhinoceros formed of black miasmic energy and demonic flames. It charged forward relentlessly, stabbing deep into the Demon’s stomach and ripping it open. Intestines spilled out as ribs shattered under the brutal assault.

CLASH! CLASH! CLASH! CLASH!

“RAAAAAH!”

Even as he was being torn apart, the Demon roared in fury and charged. He slammed his fists into the Heavenly Demon’s stomach and chest, nearly caving in his thorax and shattering three of his ribs.

CRASH! CRASH! CRASH!

The Heavenly Demon vomited blood as a broken rib pierced his lung, but he ignored the agony. He twisted his body violently, merging his blood with his aura. The burning mixture granted him a fresh surge of savage strength.

I cannot let him win! If I do, this monster will destroy everything…! I cannot lose. Not after everything we’ve been through. Not after coming this far!

His aura shifted once more, rapidly changing shape as it absorbed and embodied his pain. The Demon suddenly froze, eyes widening in shock, awe, and twisted amusement.

“W-Wha…?!”

The Heavenly Demon’s aura had transformed into an entire landscape. A world.

Visions of his brutal life unfolded within it. The pain. The suffering.

A lonely little crow struggling to survive after his entire family was slaughtered. The countless times he had been tricked, betrayed, and nearly killed.

The day he was captured by slavers, tortured, and sold as an exotic “creature,” the only red-eyed crow in existence.

The night he finally broke free, leading dozens of other slaves in a savage revolt as they tore their captor apart like rabid beasts.

How he had stepped onto the Demonic Path not by choice, but because it was the only path left in such a cruel world.

The endless chases by authorities, forcing him to hide, set traps, and kill his pursuers one by one, earning him the feared title of “Demon.”

The way his dark powers had awakened. How he had burned a malefic rune of his own creation into his own flesh, turning his suffering into strength beyond imagination.

And the moment he had stood at death’s door, cornered by orthodox cultivators and nearly slain by an immortal summoned to erase him.

Even when he finally ascended as an Immortal, he was thrown into an even more dangerous world. True peace remained forever out of reach. 

He was forced to fight without end, shedding blood simply to survive. Even after ascension, the battles never ceased. There was no future for him except dying on the battlefield. 

Through countless brutal challenges, each one forged him into the world’s Heavenly Demon, the vilest of them all. He rose as the leader of the revolutionary Demonic Cultivators, a force that defied the rigid rules and corruption of the orthodox sects and the Heavenly Court. 

After a lifetime of struggle, he finally became a Venerable, reaching the absolute pinnacle of the world. Demonic Cultivators venerated him as their God, while the rest of the world feared him as the ultimate Demon of Evil. 

And yet, at the end of that long and bloody journey, he clashed with the pinnacle of his opposite side, the one he had believed he was destined to kill. 

But he could not. 

Instead of death, Heaven itself intervened and stopped them from destroying each other. In that moment, he realized that fighting was no longer the answer. 

Although reluctant at first, as he came to know that woman, he discovered she was nothing like he had imagined. Her life had been just as filled with pain and agony as his own, marked by suffering in every stage. 

And yet… 

Why? 

Why had she chosen a different path? What had given her the strength to even make that choice? 

He had always believed that anyone born and shaped as he was would inevitably become the same: a resentful soul who wanted the world to burn so he could rebuild a new, chaotic one from its ashes.

And yet, despite facing the same hardships and enduring unimaginable suffering, she chose the opposite path. She fought against evil and helped the poor, even when she had almost nothing herself.

Despite how much he had hated her…

He could not help but feel a deep admiration for her, stronger than any he had ever felt for another person.

This woman… She was the one who had shaped his entire life from that moment onward.

His aura transformed. The Heavenly Demon’s memories, thoughts, and every painful challenge he had overcome fused into raw strength.

All of it converged within his fists as he struck the Demon before him, an ultimate evil, a true monster with no redeeming qualities. An agent of pure destruction and chaos who valued no life.

And then, the two most precious treasures in his life shone brightly through the darkness of his powers.

Song, his beloved son, the innocent soul born from his union with the Heavenly Empress, whose life had ended in tragedy.

And Anna, his adoptive daughter who had come from beyond the stars. She had saved his son and taught him the meaning of empathy.

“THIS IS ALL I HAVE!”

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