One possible motive could be Anakin's fall to the dark side. The dark side twists his perception and he might see Ahsoka as a threat to his newfound power or loyalty to the Sith. Maybe he believes she would try to stop him from achieving his dark goals.
In some fanfics, it could be due to a misunderstanding. Anakin might be misled by false information, thinking that Ahsoka has betrayed him or the Jedi Order in a significant way. His impulsive nature, which is often a part of his character, could lead him to act without fully investigating the truth first.
Another aspect could be related to the overarching plot of the fanfic's universe. For example, if there is a powerful dark entity controlling Anakin, it could force him to kill Ahsoka against his true will. This would add a layer of tragedy to the story, as Anakin would be a victim of external forces while also being the perpetrator of a heinous act against someone he once cared for deeply.
One possible motive could be power. In some fanfics, Sasuke might be driven by an insatiable thirst for power and see Naruto as an obstacle. Another could be revenge, perhaps believing Naruto has wronged him in some way in that alternate story. Or it could be a matter of being corrupted by dark forces, which make him turn against Naruto.
One possible motive could be Anakin's fall to the dark side. The dark side clouds his judgment and makes him see Obi - Wan as an obstacle to his power. He might believe that by eliminating Obi - Wan, he can fully embrace the dark side and gain more control. Another motive could be jealousy. If Anakin feels that Obi - Wan is always favored or is holding him back in some way, this could fuel his anger and lead to him wanting to kill Obi - Wan. Also, the influence of Palpatine might play a huge role. Palpatine could have manipulated Anakin into believing that Obi - Wan is a threat to the new order he wants to create.
One possible motive could be revenge. If Pauna had done something really bad to Clarke or someone Clarke cares about in the fanfic's backstory, Clarke might feel compelled to kill Pauna. Another could be self - defense. Maybe Pauna was attacking Clarke and she had no other choice.
One possible motive could be a dark or alternate universe take. Maybe in this fanfic's world, there is some sort of dark magic or mind control that forces Naruto to do it against his will.
One possible motive could be a sense of betrayal. Maybe she felt betrayed by the Jedi Order in some way and turned to the Sith for power and revenge. For example, if she was wrongly accused of something and the Jedi didn't support her.
One possible motive could be a dark magic or mind - control situation. Maybe an enemy has the power to control Naruto's actions and forces him to kill Sasuke against his will. Another could be a miscommunication where Naruto believes Sasuke has done something unforgivable, like harming the village in a way that Naruto can't overlook.
One possible motive could be power. Bowser has always been after power and ruling the Mushroom Kingdom. Maybe in this fanfic, Mario was getting too much influence or was about to discover something that could undermine Bowser's power, so he decided to kill him.
One great Ahsoka and Anakin fanfic is 'The Apprentice's Journey'. It delves into their relationship during their time as master and apprentice. It shows Anakin's complex emotions towards Ahsoka, his pride in her growth as a Jedi, and also his protective instincts. The story is filled with action scenes that they face together, and the character development is really well - done.
For the clones, it could be a confusing and demoralizing event. Ahsoka had a good relationship with many clones. Her death by Anakin, who was also their general, would make them question their loyalties and the nature of the war they were fighting. This could lead to some clones defecting or becoming more hesitant in following orders.
One possible storyline could be that Anakin, under the influence of the dark side, accidentally uses too much force during a training session with Ahsoka, physically hurting her. This could lead to a rift in their relationship as Ahsoka struggles to understand what happened and Anakin feels guilty.