Ruby has the potential to be the hero in the alternate ending. As we know, her silver eyes are a powerful weapon. If she had used them more effectively earlier in the battle, she could have been the one to stop Cinder and save Beacon Academy. She is also the main character, so it's quite likely she could take on a more heroic role in a different version of the story.
Pyrrha could be the hero. If she had survived, she could have gone on to become a more powerful huntress and a symbol of hope. Her skills and determination were already great, and in an alternate ending, she could have overcome Cinder and led the charge against the Grimm.
Ozpin could be the hero in the RWBY Volume 3 alternate ending fanfiction. He has a lot of secrets and power. If he had decided to be more upfront about his abilities and knowledge, he could have led the defense against the enemies much better. He could have used his influence to bring more help from other kingdoms and prevent the disaster that happened at the end of Volume 3.
Well, it might be that Ruby arrives in time to save Pyrrha. Instead of the tragic ending we saw, Ruby's silver eyes power could have been triggered earlier and she could have turned the tide against Cinder. Also, the relationships between the characters could develop differently. For example, Blake and Yang might not have their falling out as in the original, and they could work together more effectively to fight off the enemies.
Ruby is often very popular in alternate fanfiction. Her innocent yet determined nature makes her a great character to put in different scenarios. Blake is also popular as her complex backstory and struggle with her identity can be explored in many alternate ways. Yang too, with her strong - willed and fiery personality, often takes center stage in different fan - created stories.
One possible alternate ending could be that Twilight Sparkle uses her magic in a completely unexpected way to stop the wedding chaos and actually uncovers a plot that was much deeper than anyone thought, leading to a celebration of friendship rather than a wedding.
Well, imagine if Romeo didn't believe the false news of Juliet's death at all. He decides to go and rescue her from the tomb instead of killing himself. When he arrives, Paris is there, but Romeo manages to defeat him without killing him. Then, he wakes Juliet up, and together they run away to a far - off land where no one can find them, leaving their families behind to deal with the consequences of their feud.
In RWBY fanfiction, the hero's journey path might start with their discovery of their unique abilities. For example, they could be in a small village when they first realize they can use their semblance. Then, they might journey to Beacon Academy, like Ruby did in the original series. Along the way, they face challenges like Grimm attacks and difficult tests. They also form bonds with other characters, which help them grow both as a fighter and as a person.
Midoriya is always a great choice. In an alternate universe, say he never met All Might and didn't inherit One For All. He might have to find his own way to be a hero, perhaps by developing a unique quirk - enhancing technology. This would show his determination in a different light. Also, an AU where Midoriya is a villain could be fascinating. We could see how his intelligence and analytical skills would be used for evil, which would be a complete contrast to his usual heroic self.
In one alternate ending, Ariel might not choose to be with Prince Eric. Instead, she realizes that her true place is in the sea with her family and friends. So she gives up on the idea of becoming human permanently and returns to her mermaid form, ruling the underwater kingdom beside her father.
One alternate ending could be that Katniss and Peeta manage to convince the Capitol of the injustice of the Games through their love story. Instead of a violent showdown, they use their popularity to start a peaceful revolution. People in the Capitol start to see the tributes as humans, not just entertainment, and the Hunger Games are abolished.
One possible alternate ending could be that Doctor Strange actually manages to defeat Thanos using his magic before he can snap his fingers. Strange could have found a way to trap Thanos in a time loop or a different dimension, thus preventing the mass destruction that occurred in the original ending.
One possible alternate ending could be that Anakin Skywalker resists the dark side at the last moment. Instead of becoming Darth Vader, he uses his love for Padmé to find the strength within him to reject Palpatine's temptations. This would change the entire future of the Star Wars galaxy, as there would be no Vader to enforce the Emperor's will, and the Jedi Order might be able to be rebuilt more quickly.