One common scenario is the love triangle aspect. If Bonnie has feelings for one of the guys who is interested in Elena, it can lead to her hating Elena. For instance, if Damon shows more interest in Elena, Bonnie, who might also have a hidden crush on Damon, could start to resent Elena.
A scenario could be related to power struggles. If Elena is seen as having more power or influence in the supernatural community in the fanfic, and Bonnie feels like she is being overshadowed. For example, if Elena is a vampire with special abilities and Bonnie is a witch, but Elena's status is always put above Bonnie's, it can cause Bonnie to hate her. This can be further exacerbated if Elena uses her power in a way that Bonnie thinks is unfair or self - serving.
Often in these fanfics, Sakura might make fun of Naruto's dreams or goals in a very mean - spirited way. This constant put - down could lead Naruto to hate her. Also, if Sakura were to side with Naruto's enemies in the fanfic for some reason, like being brainwashed or having a hidden agenda, it would be a likely cause for Naruto's hatred.
A scenario could be that Sasuke blames Sakura for something that went wrong in his revenge plan. Maybe she unknowingly did something that set him back, and in his anger and single - minded focus on revenge, he starts to hate her. Another possibility is that in the fanfic world, there is a misunderstanding. Sakura is misinterpreted as being involved with someone who has wronged Sasuke, and this causes him to hate her without really knowing the truth.
In some fanfics, Bonnie might hate Elena because of jealousy. Maybe Elena always gets the attention of the male characters they both know, like Stefan or Damon, and Bonnie feels left out or second - rate in comparison.
In other cases, it could be a matter of Sonic feeling overshadowed by Tails' intelligence. Tails is known for his smarts and inventions. If in the fanfiction Sonic is feeling insecure about his own abilities, he might start to resent Tails for being so clever. This can create a rift between them and lead to Sonic hating Tails.
One common scenario could be that his family has some sort of dark secret. For example, his father might be involved in something evil that Naruto discovers, leading him to hate his family. Another scenario could be that his family has been neglectful of him. In the fanfic, Naruto might have grown up feeling unloved by his family, which causes his hatred.
One common scenario is that Harry leaves Britain and goes to live in another wizarding community. He might feel that he can start anew away from the pain and memories of Britain.
Another scenario could be that Bella does something that endangers Jacob's family or the werewolf pack. This would make Jacob see her as a liability and develop hatred towards her. In some fanfictions, she might accidentally expose the werewolves to their enemies because of her association with the vampires.
There's a fanfiction called 'Elena, Bonnie and the Forbidden Spell'. It's quite engaging as it takes the two characters on a journey to break a powerful spell. Along the way, their friendship is tested and strengthened, and the author does a wonderful job of creating a vivid and immersive world for them to exist in.
One scenario could be that Naruto discovers some hidden secrets about Minato and Kushina that he interprets as them being selfish. For instance, he might find out that they had a choice to be with him but chose something else instead, which makes him angry and full of hatred towards them.
Friendship is a common theme. Writers often show how Bonnie and Toy Bonnie become friends despite their differences. Maybe Bonnie is the more traditional character and Toy Bonnie is the new addition, and they learn to get along.