Another plot could be that his lover was a spy all along, sent by the Order of the Phoenix or some other group to get close to Voldemort. When he finds out, he feels betrayed and loses his lover in the process. This discovery could make him more paranoid about those around him and more determined to destroy his enemies.
Maybe his lover was killed by his enemies. Voldemort, despite being a dark wizard, had deep feelings for this person. His loss could make him go on a rampage to seek revenge against those who took his lover away. He might also start to question his own actions and the path he has chosen in life.
He might become more vulnerable. Usually seen as a powerful and cold - hearted villain, losing his lover could expose a softer side. He could start to show emotions like sadness or regret that he has never shown before.
One possible plot could be that Voldemort's lover discovers his true dark nature and decides to leave him. This shatters Voldemort as he realizes he has lost the one person who saw something good in him. It could lead to a downward spiral in his character, making him even more bitter and vengeful towards the world.
Another option could be a Muggle - born witch. Voldemort might have been intrigued by her in a different way compared to his hatred for most Muggle - borns. But as his views on pure - blood supremacy become more extreme, she can't bear to be with him any longer, and their relationship ends.
Well, perhaps the plot could involve a magical force that binds Harry and Voldemort together because of their past relationship. Harry might then be torn between his loyalty to his friends and the pull he feels towards Voldemort. Voldemort, on the other hand, could be using this connection to manipulate Harry, or he could also be experiencing genuine feelings that he doesn't fully understand. This could create a complex web of relationships and power struggles within the story.
One possible plot could be that Harry is captured by Voldemort and his friends have to mount a dangerous rescue mission. They might have to infiltrate Voldemort's stronghold, which could be filled with dark magic defenses.
One idea could be a fanfic where Voldemort's lover is a powerful witch who tries to redeem him. She sees the good in him that no one else does and attempts to turn him away from the dark path. They could have secret meetings in the Forbidden Forest, sharing their deepest desires and fears.
Perhaps in the fanfic, Voldemort has found a way to nullify Harry's magic for a short time. Without his magic, Harry is just a normal boy and Voldemort takes this opportunity to beat him to death. It could also be that Voldemort has an unexpected accomplice who helps him corner Harry, leading to Harry's demise.
One possible plot could be that Harry is magically compelled to submit. Voldemort might use some dark magic or a powerful artifact to control Harry's mind. Another plot could be that Harry submits out of a false belief that it will save his friends. For example, Voldemort could deceive Harry into thinking that if he surrenders, his friends will be spared. Or perhaps Harry is so worn down by the fight that he gives in, thinking there's no other way, and then the story could explore how Voldemort uses Harry's submission to his advantage, like making Harry a tool to gain the loyalty of other wizards.
One possible plot could be a moment of unexpected vulnerability for Voldemort. Maybe Draco, in a moment of courage or desperation, hugs Voldemort to show him a different side of humanity, which then makes Voldemort question his own actions.
One common theme is redemption. Maybe Voldemort has a chance at redemption through his relationship with Harry. Another theme is the power of love. It could be that their love is so strong that it can change the course of the wizarding war. Also, identity exploration is a big one. Harry has to figure out who he is now that he has this new relationship with Voldemort.