In the 'harry joins voldemort fanfic', it could start with Harry being captured by Voldemort. Instead of killing him immediately, Voldemort decides to brainwash him. Through a series of dark magic spells and psychological manipulation, Harry starts to see Voldemort as a mentor. As time passes, Harry becomes an integral part of Voldemort's inner circle, helping him plan attacks against the wizarding world, believing that they are actually for a greater good as Voldemort has convinced him.
In a 'harry joins voldemort fanfiction', perhaps Harry discovers a dark secret about the wizarding world that makes him think Voldemort was right all along. It could be something about the Ministry of Magic being corrupt and Voldemort's way of ruling, although extreme, is the only solution. So he joins Voldemort to 'fix' the wizarding world.
In this fanfic, Harry might be betrayed by the Order of the Phoenix. They could have made a decision that endangered Harry's life without his knowledge. Feeling used and discarded, Harry runs away. Voldemort, through his Death Eaters, finds Harry and manipulates him. He tells Harry that he can give him a place where he will be respected and not betrayed again. Harry, still young and naive in some ways, falls for Voldemort's lies and joins him, leading to a very different kind of war in the wizarding world.
Perhaps Harry is betrayed by the wizarding world as a whole. The Ministry of Magic wrongly accuses him of a serious crime. With no one to turn to, Voldemort approaches Harry. Voldemort shows Harry a world where he can be in control, instead of being at the mercy of those who have turned against him. So, Harry decides to join Voldemort out of desperation and a thirst for revenge against those who betrayed him.
Well, it could be that Evil Harry is actually a long - lost relative of Voldemort in this fanfiction. He discovers this connection and, feeling a sense of kinship with Voldemort's ideology of pure - blood supremacy, decides to join him. He then uses his skills at Hogwarts, like his knowledge of spells and potions, to enhance Voldemort's army. He might also be involved in turning some of his classmates to the dark side, creating a rift within Hogwarts between those who follow him and those who oppose Voldemort's new ally.
Perhaps Harry joins Voldemort out of a sense of hopelessness. After seeing so much destruction in the wizarding world, he might think that joining Voldemort is the only way to end the war quickly. However, he soon realizes that Voldemort's methods are too extreme and tries to find a way to turn things around from within the dark side.
One possible plot could be that Harry is influenced by Voldemort's false promises. Maybe Voldemort offers to bring back Harry's parents in exchange for his loyalty. Harry, in a moment of weakness and longing, decides to join him. However, once he realizes Voldemort's true nature of deception and destruction, he has to find a way to break free from this dark alliance.
Perhaps Harry joins Voldemort because he believes Voldemort's lies about the wizarding world. Voldemort could tell Harry that the Order of the Phoenix is actually trying to use him and that he would be better off with him. In this scenario, Hogwarts would become a very different place. Teachers would be in a state of panic, not knowing how to deal with Harry's new allegiance. The other students would be terrified, and some might even be swayed to Voldemort's side as well, seeing Harry as a role model. It would be a chaotic and dark situation.
One possibility is that Harry joins SHIELD after realizing the magical world can't fully contain the threats he's faced. In the fanfic, he could be a key figure in bridging the gap between the magical and non - magical worlds within SHIELD. He might introduce magic - based security measures or use his ability to detect dark magic to identify threats that normal technology can't pick up.
One possible plot for 'harry joins the military fanfic' is that Harry joins the military to find a new purpose in life. He comes from a troubled background and sees the military as a way to discipline himself. He starts in a basic training unit where he meets all kinds of different people from different walks of life. As he progresses, he discovers a hidden conspiracy within the military that threatens national security. Harry then uses his wits and new - found military skills to try and expose the conspiracy and save the day.
The Ministry of Magic could be the ones to betray Harry. They might try to use Harry as a pawn in their political games, and when Harry realizes this, he loses faith in the so - called good side. Voldemort then takes advantage of Harry's disillusionment and convinces him to join.