Well, it could be that Gladion is trying to stop a powerful, dark - type Pokemon from causing chaos. This Pokemon has some unique and deadly abilities. During the fight, Gladion misjudges the Pokemon's next move. The Pokemon uses a move that creates a dangerous environment, like a field of sharp spikes or a collapsing cave. Gladion is unable to escape in time and gets killed. Or, in the fanfiction, there could be a curse or an ancient power that targets Gladion because he has a certain item or knowledge that the force doesn't want to be in the hands of the living.
In such a fanfiction, one possible scenario could be that Gladion gets involved in a battle against a powerful and malicious Pokemon trainer. The trainer's Pokemon might use a super - powerful attack that Gladion's Pokemon can't withstand, and in an attempt to protect his Pokemon, Gladion gets caught in the crossfire and is killed. Another scenario could be that he stumbles upon a dangerous, secret organization within the Pokemon world that doesn't want their secrets exposed. They might target Gladion and assassinate him to keep him silent.
Chapter 936, "When Did the River Moon First Shine on People [Extra: River Moon Chapter]", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. Early on, Everyone, take out the test papers we didn't finish analyzing....
A practical answer is Chapter 20, because it turns the idea into a concrete scene. The chapter opens with Several people turned their heads upon hearing the sound and saw three..., adds pressure through Miss Su, please clarify the situation and do not slander me unnecessarily., and ends on So, he.
Chapter 818, "A New Village Amid Shadows and Brightness", is the clearest early answer because it turns Yu Li's situation into a concrete plot event. The chapter turns that into something concrete by moving from Wanzhi stared in shock, her eyes wide open, "What you said...
Chapter 693, "Is a Man's Prime That Short?", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter turns that into something concrete by moving from Zhao Lang had never anticipated that the bravado he had shown earlier...
Chapter 889, "Nice to meet you for the first time, please take care of me!", is the clearest early answer because it turns Gu Yu's situation into a concrete plot event. The chapter gives readers a real answer by opening on She said why do other prisoners get a chance to go outside, while she...
Chapter 940, "When Did the River Moon First Illuminate People? [Extra · River Moon Chapter]", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. The chapter turns that into something concrete by moving from Nanny Qiao, is the peach resin ready?
If you want the clearest chapter reference, go to Chapter 25. Early on, Therefore, from his childhood, Jiang Shixu had felt an extreme aversion to...; later, the chapter leans on Over time, he naturally developed a gap of estrangement between himself....
Chapter 707, "I am Daoist Qingfeng", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Su Yinwan hadn't finished her dessert but, feeling agitated, had...
Chapter 652, "He's Gu Shengrong's Grandson?!", is the clearest early answer because it turns Bai Lu's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The propellers lifted off again, and Team Q was already on their way...
Chapter 820, "He’s actually even harder to coax than Buchen!", is the clearest early answer because it turns Shi Xu's situation into a concrete plot event. It opens with Today, he was particularly cautious with his eating, even sipping his...