Garp ran toward the ship at blistering speed, Ace slung over his shoulder like a sack of cargo. He didn't slow for falling debris, clashing forces, or the chaos erupting across Marineford. Even when Sengoku's booming voice echoed behind him, carried by fury—
"Garp, get back here!"
—he didn't stop.
Ahead, Mihawk casually strolled into his path, Yoru his back. Garp braced himself instinctively, muscles tensing as he prepared to fight, but before either of them could move, a man suddenly materialized in front of him as if stepping out of thin air.
"Keep going. I shall deal with him."
Garp spared the newcomer a single sharp glance, then nodded once and surged past, vanishing into the battlefield with Ace still over his shoulder.
Mihawk's attention shifted immediately. Garp no longer mattered.
His sharp eyes locked onto the new arrival.
The stranger stood calmly before him, black hair tied neatly into a topknot, eyes as dark as coal and just as unreadable. He wore a simple white kimono and plain wooden sandals, his posture relaxed but grounded, like a mountain. As he stepped forward, he drew his sword. At a glance, it appeared to be nothing more than a plain katana with a black handle, yet the blade gleamed in the light, unmarred by even a single nick or blemish, its edge honed to absolute perfection.
Mihawk studied him carefully. At once, he knew.
This man was far from ordinary.
Stepping forward, Mihawk spoke evenly, his voice carrying a respectful curiosity.
"Before we begin, may I know your name, warrior?"
The man returned the step and offered a polite bow, calm and measured.
"I am called Jack, and I am but a humble samurai."
Mihawk's lips curved slightly as he stepped forward in turn.
"I am called Dracule Mihawk, and I am known as the strongest swordsman."
Jack smiled faintly.
"We shall see."
Mihawk smiled back, drawing Yoru in a smooth, practiced motion.
"That we shall."
The two wasted no time.
They rushed into battle, blades meeting in a thunderous clash, striking blow for blow at speeds that bordered on the unreal. Marines and pirates alike froze, watching in stunned silence as the two warriors blurred across the battlefield. Barrels, cannons, ropes, even stone beneath their feet were sliced apart by the sheer air pressure of their swings alone, steel screaming as it tore through space.
When the exchange finally broke, Jack stood unscathed, his breathing steady.
Mihawk, however, had a single cut across his cheek.
He reached up, wiping the thin line of blood away, disbelief flashing across his face before sharpening into something fierce. A wide grin spread across his features as his eyes gleamed with excitement.
"I knew I had yet to reach the peak. Even with Observation Haki, I can barely keep up with your movements. Tell me, Jack, how are you so powerful?"
Jack answered calmly, his voice steady and reflective.
"I have trained and battled for over fifty years for the sole purpose of defeating my archenemy, the demon Aku. The first time we fought, my arrogance cost me the battle, so I trained in humility. The second time we fought, he ran away before I could strike the final blow, so I trained my speed. The third time we fought, he moved into the air out of my reach, so I trained in acrobatics until I could soar through the air."
Mihawk nodded slowly, understanding dawning in his eyes.
"I see. Your enemy continuously exposed and took advantage of your flaws, so you trained them away each time. Were you ever able to achieve victory?"
Jack's smile softened, carrying both pride and sorrow.
"I was, though at a cost. I lost someone dear to me. But fortunately, in exchange for my participation in this battle, they have been brought back."
Mihawk inclined his head slightly.
"I am glad for you, then, and even more grateful to your benefactor. Were it not for them, I wouldn't be able to face you today."
Without another word, the two swordsmen surged forward once more, blades flashing as they re-engaged in their heated battle, the clash of steel echoing across Marineford like a challenge to the world itself.
-------
Garp continued his charge toward the ship, boots hammering against shattered stone, only to find his path blocked once again by a Warlord. This time, it was Gecko Moria, his shadow stretching grotesquely across the battlefield.
Fortunately, just like before, Garp didn't have to stop.
A sudden presence emerged between them, and a stranger's voice urged him onward. Garp didn't hesitate. He powered past without looking back.
The person left behind was a small woman with deathly pale skin and neck-length black hair that framed her sharp, amused expression. Violet eyes gleamed beneath two crimson horns curving from her head. She wore a short, open purple kimono trimmed with red accents, barely concealing black leather underwear beneath. Black leather greaves hugged her legs, demonic faces carved into the knees, and black leather sandals completed her attire. In one hand, she carried a massive greatsword with a large blue wine gourd tied to the handle. In the other, she casually held a red sake cup.
Moria stared at her, confusion and irritation twisting his face.
"What the hell are you supposed to be, a demonic stripper?"
The woman's only response was a giggle.
She vanished.
Moria's eyes darted wildly as he spun in place, searching for her. Before he could react, she reappeared directly in front of him and drove a brutal, bone-shattering kick into his face. The impact sent him rolling violently across the battlefield, debris flying as he skidded to a halt.
She looked down at him as one might regard an insect beneath their foot. A soft chuckle escaped her lips.
"My name is Shuten Douji. Remember it as I send you to hell."
Moria groaned, shaking off the pain as he staggered back to his feet.
"Oh screw this."
He turned and tried to flee.
Shuten appeared in front of him in a blur, her greatsword flashing as she slashed open a massive wound across his chest. Blood sprayed across the ground as Moria screamed and clutched at himself, staggering backward in agony. He tried to run again, desperation overtaking fear, but Shuten calmly lifted her sake cup and took a sip.
She exhaled.
A thick purple mist poured from her lips, rapidly swallowing the area. Moria inhaled it before he could escape. His legs buckled. He collapsed to his knees, gasping, clawing at his throat as suffocation set in.
Through the haze, he heard Shuten's terrifying laugh.
"How does my poison mist taste?"
"Poison?" He Said.
"It's quite deadly, I'm afraid. Do you have any last words?"
"This isn't fair." Said Moira.
Shuten laughed one final time, raised her blade, and cleanly decapitated Moria, ending his suffering in an instant.
She flicked the blood from her sword and sighed lightly.
"I would have played with you more, but you were weaker than I thought you'd be."
------
As Garp continued to run toward the ship, he suddenly skidded to a halt. This time, it wasn't an enemy blocking his path. A chorus of screaming echoed from above.
He looked up just in time to see a Marine battleship falling straight out of the sky.
His eyes widened as figures began tumbling down alongside it. Buggy the Clown. Ivankov. Several other prisoners from Impel Down. And then, unmistakably, both he and Ace spotted a familiar straw hat.
In unison, Garp and Ace shouted, "Damnit, Luffy!"
Luffy crashed down hard in front of them, slamming into the ground before scrambling to his feet, arms flailing as he tried to regain his balance.
"Hey, I survived!"
His declaration was immediately cut short as both Garp and Ace slammed him into the ground with brutal force, their fists connecting at the same time.
Again, in perfect unison, they shouted, "Why the hell are you here, you moron?!"
Clutching his head and groaning in pain, Luffy looked up at them and said, "I'm here to save Ace."
"I'm already doing that. Never mind. Get running to the ship. We're getting the hell out of here!!!" Garp Shouted.
Without waiting for a response, Garp and Ace each grabbed one of Luffy's arms and hauled the still-confused pirate to his feet, dragging him along as they sprinted toward the ship ahead.
Up ahead, they spotted Aokiji casually strolling into their path, hands in his pockets, expression unreadable.
Garp didn't even slow down.
"Ignore him. Someone else will handle it."
Right on cue, Aokiji was violently kicked out of their path by a figure they didn't recognize, his body skidding across the ground.
They kept running as Garp shouted over his shoulder, "Thanks, stranger!"
The figure gave them a simple thumbs-up before turning back toward Aokiji.
The warrior stood in silence, clad in heavy armor scorched with ash and flame. A red-hot, coiled sword rested across their shoulder, heat rippling the air around it. Without a word, they fixed their gaze on Aokiji and calmly prepared for battle.
(Authors Note: I'm going to preemptively answer your question yes samurai Jack can take mihawk he regularly faces a reality warping super demon and wins)