The serpent hissed as Luffy dodged another strike, his feet skidding across the mist-covered floor of the cavern. He grinned despite the intensity of the battle. "You're tough, but I don't plan on losing today!"
Luffy stretched his arms back, preparing for another punch, but the serpent's enormous head lunged toward him with terrifying speed. Luffy barely avoided it, leaping backward just in time. The cavern seemed to shake with every move the creature made, its body like a tidal wave of muscle and scales.
"Alright, time to finish this!" Luffy yelled, pumping his fists in the air. He focused all of his strength into his legs and charged, his body expanding with the force of his attack. "Gomu Gomu no Jet Gatling!"
His fists rained down on the serpent's head, the rapid barrage of blows creating shockwaves that rocked the cavern. The serpent screeched in pain, its form writhing as Luffy continued his assault. With one final, powerful punch, Luffy's fist collided with the creature's skull, sending it crashing to the ground in a heap of shattered stone and dust.
The serpent, now defeated, faded into the shadows. The massive stone door before Luffy slowly creaked open, revealing the path forward. Luffy stood there, panting but smiling proudly.
"That was fun! Time to catch up with the others!" he cheered, running through the now-open door.