character kills themselves at the end of story

It could be a fatal disease that strikes him down.

It could be a fatal disease or a tragic accident. We need more context to be sure.

One reason could be overwhelming despair. Maybe they've lost everything they hold dear, like their loved ones or their purpose in life. For example, in some stories, a character might have witnessed the destruction of their homeland and with no hope of rebuilding, they choose to end their life.

There were a few Xianxia novels with decisive protagonists that were worth recommending. Amongst them," The Battle of the Great Dao " was a fantasy Xianxia novel that focused on the fight for resources. The protagonist was decisive in killing, both wise and brave, and constantly worked hard to pursue the Great Dao. The plot of this novel was compact, the writing was smooth, and the characters were lively. It was suitable for readers who liked traditional Xianxia novels. In addition," Immortal Mortal " was also a Xianxia novel that was decisive in killing. The protagonist relied on his methods and brains to advance bravely, cutting through the clouds and thorns, showing the image of a strong person. The plot of this novel was reasonable and the writing was excellent. In addition," Evergreen Immortal Dao " was also a Xianxia novel with a decisive protagonist. The protagonist took one step at a time in the world of cultivation, breaking through all kinds of difficulties and finally achieving Dao. This novel was based on the cultivation of the family. The plot was plain but charming. These are the recommendations of a few Xianxia novels where the main characters kill.

Well, that could be a mystery until you reach the end. Maybe it's a surprise twist that the author intentionally keeps hidden until the very last pages.