His orphan upbringing is key. Growing up without parents, he lacked love and support, which might have contributed to his later evil nature. Also, his time at Hogwarts where he delved into dark magic. And of course, the discovery of his connection to Salazar Slytherin, which influenced his beliefs in pure - blood supremacy.
Tom Riddle, who became Voldemort, had a difficult start. His mother's family was related to Salazar Slytherin. In Hogwarts, he was sorted into Slytherin house. He started exploring the Chamber of Secrets, which was created by Slytherin. His thirst for power grew over the years. He split his soul into multiple Horcruxes in his quest for immortality. This act of dark magic made him more and more inhumane and led to his many evil deeds, like the murders of many witches and wizards.
One possible fanfiction could be where Harry uses a powerful, ancient magic that he discovers in a hidden chamber at Hogwarts. This magic has the power to reverse death, but he doesn't fully understand the consequences. So, when he brings Voldemort back, Voldemort is initially weak and Harry tries to keep him in check while learning more about this new situation.
Well, in the original story, Voldemort is the main antagonist that Harry is trying to defeat. But in a fanfiction where Harry brings him back, the power dynamic completely changes. Harry becomes the one responsible for Voldemort's return, which would create a whole new set of moral and ethical dilemmas for Harry. He would no longer be just the 'chosen one' to defeat evil, but also the one who brought it back.
In some fanfictions, Voldemort wins through a change in the prophecy's interpretation. If the prophecy was misread, it could give him an edge he didn't originally have.
Here's a different take. Voldemort could fall in love with a Muggle - born witch who has a special power. She might be a healer, with the ability to soothe even the darkest of souls. Voldemort, in his search for immortality, discovers her. At first, he wants to use her power, but as he spends time with her, he begins to feel something he's never felt before. He starts to protect her from other Death Eaters who might want to harm her for being Muggle - born.
Voldemort was born Tom Marvolo Riddle. His mother, Merope Gaunt, used a love potion on his father, Tom Riddle Sr. When the potion's effect wore off and his father abandoned them, his mother died soon after giving birth. Tom grew up in an orphanage. He was a very intelligent yet troubled child. He discovered his magical abilities early on and was able to manipulate those around him. His dark path began as he delved deeper into the Dark Arts at Hogwarts, influenced by his Slytherin heritage and his own thirst for power.
Tom Riddle, who would become Voldemort, was the product of a rather tragic and complex origin. His mother was from the Gaunt family, known for their inbreeding and instability. Merope's use of a love potion on Tom Riddle Sr. was a desperate act. At the orphanage, young Tom showed signs of his extraordinary magical abilities early on. His disdain for his Muggle father and his desire to rise above his humble beginnings, combined with his dark tendencies, set him on the path to transform into the feared Voldemort. He began to explore the Dark Arts, and as he grew older, he shed his identity as Tom Riddle and adopted the name Voldemort, a name that would strike fear into the hearts of the wizarding world.
Voldemort, initially Tom Marvolo Riddle. His early life in the orphanage was marked by loneliness and a sense of superiority due to his magical abilities. Once at Hogwarts, he was drawn to the secrets of the Dark Arts. He had a fascination with the concept of immortality, which led him to create Horcruxes. His rise to power was filled with bloodshed. He formed the Death Eaters, a group of Dark wizards and witches who carried out his evil deeds. He targeted Harry Potter from the start because of a prophecy that said Harry could be his downfall. Throughout his life, he was consumed by his hatred for Muggles and those who opposed him. In the end, his overconfidence and the power of love and friendship that Harry represented led to his defeat.
In many fanfictions, Bellatrix is often depicted as extremely loyal to Voldemort. She is seen as his most devoted follower, willing to do anything he asks without question.