There could be a fanfic where Harry is tricked into believing that Voldemort is the only one who can save the wizarding world from a greater threat. For example, a new, more powerful dark force emerges and Voldemort convinces Harry that they need to join forces. In this type of fanfic, Harry would gradually turn towards Voldemort's side as he is deceived by false promises.
Some fanfics in this genre might explore a world where Harry has a different upbringing. For instance, if he was raised by Death Eaters who influenced his view of the wizarding world from a young age. This different upbringing could cause him to have more sympathy towards Voldemort's cause and eventually turn to him.
One possible 'Harry saved by Voldemort' fanfic could be one where Voldemort has a sudden change of heart due to some long - forgotten magic or prophecy. Maybe he realizes that Harry's life is crucial to maintaining the balance of the wizarding world in a way he hadn't foreseen.
Well, a great voldemort captures harry fanfic is 'The Snare of the Dark Lord'. In it, Voldemort uses a powerful dark spell to paralyze Harry and capture him. The story then delves into Harry's internal struggle as he tries to find a way to break free. Another fanfic could be 'Imprisoned by Voldemort' which focuses on the psychological battle between Harry and Voldemort while Harry is held captive. And 'Under Voldemort's Control' is also a good one where Voldemort tries to turn Harry to the dark side while having him captured.
One interesting Voldemort fanfic could be those that explore his early years before he became fully evil. Maybe a fanfic where we see his time at Hogwarts and how his dark thoughts started to form. Another could be a story where Voldemort has a chance at redemption, which is quite a different take on his character. And there are also fanfics that focus on his relationship with his Death Eaters in more depth, showing the power dynamics and loyalty within the group.
One popular 'Harry kills Voldemort' fanfic might be the one where Harry uses a unique spell combination that he discovers in an ancient magic book hidden in Hogwarts. This spell gives him an edge over Voldemort's dark magic.
One popular 'Harry Turns Dark' fanfic could be 'The Darkened Heir'. In this type of fanfic, often the author explores how Harry's experiences could have pushed him towards the dark side. Maybe the betrayal he faced from some in the wizarding world made him bitter. Another could be 'Dark Harry's Ascent' where the story might show how Harry uses dark magic to get revenge on his enemies. And there's also 'Harry: The Dark Lord Reborn' which could play with the idea of Harry taking on a more sinister role similar to Voldemort but with his own motives.
I'm not sure specifically which 'Harry Spreads for Voldemort' fanfics are popular. You could try searching on major fanfic platforms like Archive of Our Own or Fanfiction.net and look for ones with high ratings and a lot of reviews.
The deviation from the original story makes it unique. In the original 'Harry Potter' series, Harry is the hero against Voldemort. But in these fanfics, the roles are being reversed in a sense, which is a huge departure from the norm.
One popular one might be 'The Stolen Boy' where Harry is taken from Voldemort's clutches in a very unexpected way. It has a unique plot where the wizarding world has to deal with the consequences of Harry being in a different situation than in the original story.
I'm not sure about a specific title, but in general, fanfics in this category often play with the idea of Voldemort's control over his followers. They might show how characters are forced to do his bidding, like in some where he uses dark magic to enslave wizards. However, this is a rather dark concept within the Harry Potter fanfic realm.
One common theme is redemption. In these fanfics, Harry's love often serves as a catalyst for Voldemort to potentially be redeemed. It's about the idea that love can break through even the darkest of souls.