[This is an idea that came to me when I was reading another fan fiction]
Kid was fuming; the cowardly Marine hiding behind a tree was his target. That man was the reason why Trafalgar wasn't eating or talking. He was the reason why his lover doesn't acknowledge his presence anymore.
That marine soldier was why Trafalgar seemed as if he didn't know his surroundings. He was going to pay. Kid jumped off the Thousand Sunny, running towards the battlefield impaling a marine who was shooting at him with a piece of metal. He kept his gaze focused solely on that marine, who began running when he noticed Kid charging at him. Seeing him run only spurred Kid on who reveled in the chase, it seemed the marine was injured as he only managed to hobble a few feet away from the tree he was hiding behind.
Kid grabbed the marine's arm -who struggled and writhed in Kid's grip trying to break free-and squeezed tightly with his metal hand. Feeling more than hearing the bones break. The unidentified man howled in pain, feeling the bones in his arms break as the redhead pirate somehow tightened his grip till the marine thought he was going to pass out from the pain, black spots swimming in the corners of his eyes. Kid threw the soldier to the ground watching as he tried to stand, he placed one heavy foot on the man's spine and pressed down with half his weight. The man underneath his boot let out a blood-curling scream as he felt Kid attempt to snap him in half; suddenly the intense pressure on his spine was gone as Kid had removed his weight off the smaller man. Kid bent down, using his human hand he flipped the marine on his back and ripped his pants off with his metal hand, turning him around once more kid pinned the soldier down with his human hand before growling to the man "Payback's a bitch" and shoving two cold metallic fingers up the man's entrance.
The marine screamed feeling unimaginable pain race from his asshole to his whole body ;he was torn badly: Kid pushed his fingers deeper when the man began squirming trying to run away from the intrusion down below, using the blood as lubricant Kid shoved another metallic finger up his ass, and another, and another till his thumb remained. The marine soldier screamed even louder as he felt his ass get literally split wide open by the metallic fist going in, Kid with his huge fist inside the man's ass pushed deeper till a quarter of his muscular forearm had slipped the bloody passage, causing the marine to vomit as the pirate attempted to uncurl his fist inside him. The captain pulled his fist out tearing his ass even more before shoving nearly his whole arm into the marine once more, making him piss all over himself as the pirate managed to uncurl three of his fingers and dragged them roughly over what he believed to be the large intestine making the drained marine scream hoarsely, he cried as Kid's hand went till his elbow before pulling it out and shoving it back in over and over.
Kid used his Devil Fruit power to attract a 6 meter long pipe, he noticed one point was sharp he pulled his arm out and shoved the pipe inside, the marine screamed as he felt something sharp and cold touch his gaping asshole but it became a bone-chilling scream as the redhead captain shoved the whole pipe in piercing his intestines and push through his stomach. Kid stepped back and looked, he looked at the marine with a gaping asshole and a pipe pierced through him, the blood pouring out in volumes before turning his back to the scene and making his way to Thousand Sunny. Kid heard the Straw Hat captain calling him, getting louder as the black-haired male came closer. Luffy found Kid with bloody hands and a sickening grin on his lipstick-covered lips, the look in the redhead eyes was sick joy and fulfillment, the Straw Hat captain instinctively moved back a bit but asked him "Kid, what happened?" "Nothing, Straw Hat. Where's the reindeer?" "In the kitchen with Sanji." Kid walked past Straw Hat heading to the kitchen to get the reindeer to clean him up, leaving Luffy there staring at his back in shock by the amount of blood on the other pirate's arms and bits of skin and the look of twisted accomplishment.
The redhead captain sat beside Trafalgar, just staring when Trafalgar shifted and opened his eyes slowly, his gaze unfocused stared at the ceiling of Chopper's infirmary before turning his head and noticed Kid there staring at him intently. He sat up and stared back at the other pirate before breaking the silence "You killed him" it wasn't a question but kid still answered like it was "Yeah, how could you tell?" "You smell like alcohol" "Oh". Trafalgar rose from the bed and stood in front of Kid, who had looked down at his arms while Trafalgar slowly wrapped his arms around his lover's neck and tilted his head to look him in the eyes before placing a kiss on Kid's lips and whispered "Thank You" almost inaudibly. Kid looked at Trafalgar's face: his sharp cheekbones, his pointy nose, his gray stormy like eyes and his thin lips: memorizing that moment into his brain before closing his eyes and pulling Trafalgar into him and kissing him deeply.
Breaking the kiss Kid placed his head in Law's chest as the aforementioned man wrapped his arms around Kid neck once more and they stayed like that for what could have been minutes till Chopper came in saying Trafalgar had to eat and a talking polar bear kept apologizing and two men in white jumpsuits insisted to see Trafalgar. Trafalgar removed his hands from kid's neck and said to Chopper "It's ok, they're my crew", Kid took that as his cue to leave and exited the room to look for Killer. Killer heard the heavy footsteps approaching and the body slide into the seat next to him, Killer turned his head to his captain but seeing Kid look into the vast ocean with a blank look he turned and looked at the ocean, they stayed there in comfortable silence before the weird curly-eyebrow cook called them for dinner.