It could also be that Qrow's death is related to his own self - destructive tendencies. His alcoholism and the constant negative effects of his semblance on his psyche might lead him to make a rash decision. For instance, he might feel that he's a burden to his team or family because of his semblance always attracting bad luck. So, he decides to go on a solo mission against impossible odds, fully expecting not to come back alive.
One possible plotline could be Ruby learning combat skills directly from Qrow. Since Qrow is a skilled Huntsman, he could teach Ruby unique fighting techniques that she might not have learned otherwise. For example, Qrow could show her how to use her scythe in more unconventional ways, taking advantage of her small stature and speed.
One possible plotline could be that Ruby sacrifices herself to save her friends from an overwhelming enemy. In the heat of battle, she realizes that only by giving up her own life can she ensure the safety of her team. Another could be that she is poisoned by a new and deadly Grimm toxin that slowly weakens her until she passes away, leaving her friends to avenge her.
One possible plotline could be that Ruby's death shatters her team. Weiss might become overly consumed with vengeance, leading her to make hasty and dangerous decisions. Blake could retreat into herself, feeling like she failed to protect Ruby. Yang might struggle with survivor's guilt and question her own strength. Another plotline could involve Ruby's sacrifice being the key to saving Remnant. Her death could inspire the remaining characters to come together in a way they never had before, uniting the kingdoms against a common enemy like Salem.
One plotline could be Ruby's death leading to a power vacuum. Since she's a powerful and important figure in the RWBY world, her death could cause chaos. Her friends might struggle to fill the void she leaves, both in terms of leadership and combat ability. For instance, they might have to quickly learn to work without her Crescent Rose and her strategic mind.
Another plotline might be the bringer of death's journey of redemption. They start off as a cold - blooded killer but then meet someone or experience something that makes them question their ways. They could then try to use their powers for good, which would be a difficult transition as they are feared by many. This could create a lot of internal conflict within the character as well as external conflict with those who don't trust their change of heart.
Perhaps in the 'rwby pyrrha returns fanfic', Pyrrha returns with a mission to redeem herself. She could have made some sort of deal during her absence that now requires her to complete certain tasks to save Remnant. This would involve her working with RWBY and other allies, while also dealing with the mixed feelings her friends have about her return.
In RWBY fanfiction, Qrow's alcoholism is often a complex and interesting aspect to explore. It can be seen as a coping mechanism for the difficult things he has faced. Writers might use it to show his internal struggles and how it affects his relationships with other characters, like Ruby and Yang.
Maybe in the fanfic, Death is not a traditional Grim Reaper - like figure but rather a form of an evil curse that has been plaguing the ninja world. Naruto, being the hero, is the only one with enough positive energy and determination to face it. He could start by gathering allies who have also been affected by this 'Death' curse. Together, they form a plan. Naruto would be the vanguard, using his speed and strength to break through the defenses of the curse - based Death and then use his willpower to shatter it completely.
One possible plotline could be that Cinder discovers a pair of garnet pants with some sort of magical property. Maybe the pants give her an extra boost in her combat abilities, and she has to keep it a secret from the other characters while using it to her advantage in battles against RWBY and their allies.
One interesting Uncle Qrow fanfic could be those that explore his relationship with Ruby. For example, a fanfic might focus on how he trains Ruby in secret combat techniques, adding more depth to their family bond.