As the teaching progresses, they could develop a sort of mentor - mentee relationship. Harry would be constantly trying to steer Tom away from the Dark Arts, while Tom would be trying to learn as much as he can from Harry. However, there would always be an underlying tension because of Tom's future as Voldemort. Their relationship might be a complex dance of trust and suspicion.
Maybe Harry would teach Tom about the consequences of dark magic. Since Harry has faced Voldemort multiple times and seen the destruction caused by dark spells. He could use these real - life (well, in the wizarding world) examples to make Tom understand that there are other paths in magic that are more positive and life - affirming.
One possible plot could be that Harry, using his knowledge of love and friendship, tries to teach Tom about the power of positive emotions. He might show Tom how his own journey was shaped by the love of his friends and family, in contrast to Tom's more solitary and power - hungry path. Maybe Harry takes Tom to Hogwarts in a time - travel like scenario and shows him the true meaning of the houses, not just the pursuit of power within Slytherin.
A lot could occur. Harry might try to instill in Tom the importance of forgiveness. Given that Harry has forgiven many of his enemies, he could explain to Tom that holding grudges and seeking revenge only leads to more pain and destruction. For example, when he forgave Snape in the end.
Well, it could be that Harry's hands - on experiences from his own time at Hogwarts make his teaching really engaging. He might share his encounters with dark creatures and how he overcame them. This could make Tom more aware of the practical side of DADA.
Harry would be really interesting. He has to step into the role of a teacher, which is quite different from his usual role as a student or a hero. He has to figure out how to communicate with Tom, who is essentially the most evil wizard in history. Harry's own experiences with Voldemort give him a unique perspective, and seeing how he uses that to try and teach Tom would be fascinating.
One possible plotline could be that Harry, with his knowledge of the Dark Arts from his own experiences, tries to show Tom the true nature of defensive magic. He might start by teaching basic spells like the Shield Charm. Harry could also share his insights on how to resist the allure of the Dark Arts, which is something Tom struggles with in his later years as Voldemort.
Maybe there will be a competition or a test in the DADA class that Harry is teaching. Tom could either shine or struggle, and this could affect his relationship with Harry. If he does well, he might gain more respect for Harry and DADA. If not, he could become determined to improve.
One great 'Harry Potter Tom Riddle Fanfiction' is 'The Heir of Slytherin's Redemption'. It shows a different side of Tom Riddle, exploring what could have happened if he had been given a chance at a different path. It has a really interesting plot that keeps you hooked from start to finish.
One popular idea in such fanfiction could be that Harry, through some magical time - turning or alternate reality scenario, discovers Tom Riddle before he fully becomes Voldemort. Harry might see the good in Tom that was lost over time and tries to prevent his fall to the dark side. Their soulmate connection could be a powerful force that draws them together, even as their destinies seem so opposed.