Well, if Anakin never turned, then the Sith's long - term plan would have been in shambles. The Sith had been plotting for a long time to take over the galaxy through Anakin's fall. Without that, the balance of the Force would have remained more in favor of the light. Anakin could have been a great Jedi Master, training new generations of Jedi. His skills and power on the light side could have been used to fight other threats in the galaxy. And there would have been no need for Luke to redeem his father, as Anakin would have always been on the right side of the Force.
If Anakin hadn't turned, the Sith's plans might have been foiled. The balance of power would have remained with the Jedi, and galactic conflicts could have been avoided or resolved differently.
Well, the galaxy would have been a much more peaceful place. The Jedi Order might have remained strong, and there would likely have been no rise of the Empire.
If Anakin never turned, Luke and Leia would have grown up with their father. The Skywalker family would be united, and they could all be trained as Jedi. This would make them a powerful force for good in the galaxy. Also, the Sith would likely have a harder time achieving their goals without Anakin as Darth Vader.
Well, if Anakin didn't turn to the dark side, the Clone Wars would probably have ended differently. Anakin was a key figure in many battles during the Clone Wars. His continued loyalty to the Jedi could have meant a more decisive victory for the Republic. The Sith plot to create the Empire through the Clone Wars would have been foiled. And the relationship between the Jedi and the clones might have evolved in a more positive way. Anakin could have used his influence to improve the treatment of the clones, and they could have become an even more integral part of the Republic's defense force rather than being turned against the Jedi as they were when Anakin turned.
One possible plot could be that Anakin continues to be a Jedi and plays a crucial role in bringing more peace to the galaxy. He might focus on training new Jedi, using his unique skills and powers for good. For example, he could be sent on diplomatic missions, using his charisma to convince planets to join the Republic without the need for military force.
If Anakin never turned to the dark side in comics, the Jedi Order could have remained strong and continued to maintain balance. Maybe he would have become a great Jedi Master and trained many new padawans.
One way to write it is to focus on Anakin's positive relationships. For example, if his bond with Obi - Wan was strengthened even more, it could prevent his fall. The fanfic could show more of their training sessions together, with Obi - Wan guiding Anakin through his inner turmoil in a more effective way.
You might want to check out 'Anakin's Steadfast Light'. Here, Anakin is faced with numerous temptations but always manages to resist, thanks to the support of his friends and his own inner resolve. The plot is full of close calls and challenging situations that test his commitment to the light side, but he never gives in.
If Naruto turned to the dark side in a Star Wars fanfic, his shadow clone jutsu could be used in a very menacing way. He could send shadow clones to infiltrate Jedi or Sith strongholds. His Rasengan, with the added dark side energy, might become a more destructive and unpredictable force, like a mini - black hole of sorts in the Star Wars context.
If Anakin never turned to the dark side in the fanfic, the galaxy would be a very different place. The Clone Wars might have ended sooner, as Anakin's strategic brilliance could have been fully utilized for the good of the Republic. He would still be a symbol of hope for the Jedi and the people of the galaxy. His friendship with Obi - Wan would have remained strong, and they could have achieved great things together as a team of powerful Jedi.