There were novels where the main characters would go to hell and be reborn. These novels were often called the " Hell Rebirth Stream " or the " Dark Stream." The more famous ones included:
1 " Lord Snow Eagle ": The protagonist of the novel, Ye Fei, is an ordinary game player. However, he accidentally transmigrated to a world similar to a game. This world is ruled by an evil force, and Ye Fei's mission is to save this world. In the process of saving him, he encountered many difficulties and dangers. In the end, he became the leader of this world through constant fighting and hard work, and obtained the power of rebirth in hell after death.
The main character of this novel, Wei WuXian, is a Xianxia character who accidentally transmigrated to a world full of magic and monsters. In this world, he made many friends and enemies, and gradually grew up through constant adventures. In the final battle, he chose to go to hell to be reborn in order to save the world. After rebirth, he became an even stronger existence.
[3. Douluo Continent: The main character of this novel, Tang Wulin, is a soul master. He accidentally transmigrated into a soul master's world.] In this world, he had become a powerful soul master through constant cultivation and battle, and he had obtained the power of hell's rebirth after death.
The protagonists of these novels all experienced a lot of pain and setbacks, but after being reborn in hell, they became stronger and wiser beings to continue their mission.
Maybe Naruto goes to hell to rescue a friend or to face some powerful dark forces. For example, he might go to save Sasuke who got trapped there somehow.
Obviously, Katherine would be one of the main characters as the story is centered around her time in hell and what happens after. Damon and Stefan would also be important as they have a long history with Katherine. Their reactions to her return would be crucial to the plot.
One possible plot could be Katherine coming back from hell with new powers. Maybe she seeks revenge on those who wronged her before. She could target Elena specifically, creating a lot of chaos in Mystic Falls.
The main antagonist could be the Devil himself. He might see Harry as an intruder in his domain and try to keep him there forever. He could set up all kinds of traps and challenges for Harry to overcome.
One possible plot could be that Harry is sent to Hell due to a powerful dark magic spell gone wrong. In Hell, he has to face his worst fears and demons, both literal and metaphorical. He might encounter lost souls who tell him secrets about the magical world. Eventually, he manages to find a way back, using his wits and some unexpected magical abilities he discovers during his ordeal.
Perhaps she forms an unlikely alliance with other damned souls in hell. They might work together to try and find a way to escape or at least improve their situation in hell. It could involve some sort of power struggle among different groups of souls in the hellish realm.
It's possible that she'll form new relationships in hell that will change her. For instance, if she meets a soul who was a victim of her actions on Earth, she could be forced to confront the consequences of her actions directly. This could lead to a transformation in her personality, either towards redemption or further into villainy depending on how she reacts to these new relationships.