The Dark Dark Fruit could enhance Luffy's physical strength in a different way. Instead of just relying on his rubber body, the fruit's power could give him a more menacing presence in battle. He could use the darkness to absorb attacks and then redirect that energy, making his counter - attacks even more powerful. For instance, if an enemy throws a punch, Luffy could use the dark power to suck in the force of the punch and then send it back double - strength.
His leadership style could change significantly. In the original, he leads with his heart and by example, but in a dark fanfiction, he could be more of a dictator - like leader within his crew, making decisions without much input from others and demanding strict obedience. His goals might also shift from just finding the One Piece and having a grand adventure to seeking power for more self - centered reasons, like revenge or dominance.
In such a fanfiction, perhaps Luffy's character would change drastically. The dark dark fruit might give him new powers like controlling shadows more intensely than Blackbeard. He could use it to create shadow clones of his crew for strategic battles, adding a new and darker dimension to his fighting style.
The World Government could become the main antagonist. They would see Luffy's new power as a threat, especially if he starts using it in ways that oppose their rule. They might send out their strongest agents, like the Admirals, to take Luffy down. The Admirals could have developed new techniques to deal with the dark dark fruit powers, making them a formidable foe for Luffy.
One interesting concept could be Luffy having to deal with the corrupting influence of the Dark Dark Fruit. Maybe he struggles to maintain his usual carefree and positive attitude while using its powers. For example, the power might make him more withdrawn at first as he tries to figure out how to control it without losing his sense of self.
Often, in fanfiction about Power Dark Luffy, the story might deviate significantly from the original One Piece plot. Writers may explore different power-ups for him. His new 'dark' powers could be related to shadow manipulation or some sort of dark energy. This not only changes his appearance but also his fighting style. His relationships with other characters in the One Piece universe would also be affected, leading to new and exciting storylines.
In some 'dark luffy fanfiction', Luffy could be possessed by an evil entity. This entity twists his mind and makes him see his friends as enemies. So, he begins to attack the people he once cared for deeply. The crew has to find a way to save Luffy from this dark influence without hurting him, which creates a lot of tension and drama.
Well, I'm not sure specifically which 'luffy dark lemon fanfiction' is the best. But generally, a good one might be the one that manages to blend the 'dark' elements in a way that still respects the core of Luffy's character. Maybe it shows Luffy having to make tough moral choices in a dark setting, which is different from his usual carefree self in the official story. But remember, this is a very niche area of fanfiction.
There are several places you can look for 'luffy dark lemon fanfiction'. Fanfiction.net used to be a great place to start, but they have certain content guidelines. Archive of Our Own (AO3) is also a popular site among fanfiction writers and readers. You can search for 'luffy dark lemon' there. Just be aware that not all works will be of high quality, and you may need to sift through a lot to find something that interests you.
One interesting concept could be a darker version of Luffy's leadership. Instead of his usual carefree and positive leadership, it might show a more calculating and perhaps even ruthless side in making decisions for the crew's survival in extremely tough situations.