A third theme could be transformation. The villain may transform into a better version of themselves. In the case of 'Twilight', Edward tries to control his vampiric instincts because of his love for Bella. His 'villainous' side related to his blood - thirsty nature is subdued by his love for her, showing how the hero's love can bring about change in the villain.
A frequent theme is the power of love to change. The love the villain has for the hero can make them question their entire belief system. Also, there's the theme of secrecy. Since they are from opposing sides, they often have to keep their relationship a secret, which adds a lot of tension. In some fanfictions, this secrecy is what drives the plot forward, as they try to hide their feelings from their respective allies.
The exploration of good and evil is also a big theme. In 'Grendel', we see that the line between good and evil is not so clear. Grendel is not simply a villain, and through his story, we question what truly makes a hero or a villain. Often, these novels also deal with themes of social outcast. The characters start as outcasts, like the wrongly imprisoned Edmond Dantes, and they rise above their circumstances to become heroes.
Well, power is often a theme. The hero and the villain might be vying for power, whether it's political, magical or just over a group of people. Also, the theme of sacrifice can be present. The hero may have to sacrifice something dear to defeat the villain.
One common theme is the struggle between good and evil. The hero represents all that is good, like justice and kindness, while the villain stands for greed, power - hunger or malice. Another theme can be redemption. Sometimes the villain has a chance to turn good, or the hero might face a moral dilemma that tests his own 'hero - ness'. Also, the theme of sacrifice often comes up, where the hero might have to give up something precious to defeat the villain.
Self - discovery is also common. As the villain turns into a hero, they often discover new aspects of themselves. Snape in 'Harry Potter' discovers his true loyalties and the kind of person he wants to be in the face of his love for Lily. He transforms from a seemingly one - dimensional 'bad guy' to a complex and ultimately heroic character through this self - discovery process.
One common theme is the battle between good and evil. The hero represents good and tries to stop the villain who represents evil. For example, in many stories, the hero fights to protect the innocent from the villain's harm.
The challenges are numerous. There's the matter of loyalty. The hero has loyalty to the good side and the villain to the bad side. How can they reconcile this? Then there's the power dynamic. If the villain is more powerful, the hero might be in a vulnerable position. Also, they have different goals in life. The hero wants to save the world, while the villain may want to rule it. This disparity can cause a lot of problems in their relationship.
The theme of self - discovery also exists. The villain may discover new aspects of themselves through their love for someone else. Their love can be a catalyst for them to question their own identity and motives, leading to a transformation in their character.
Another theme is the power of friendship, but in a twisted way. Sometimes Izuku as a villain has a group of loyal followers or partners who are with him not because he's a hero, but because they share his view of the world. It shows that even in villainy, there can be strong bonds between characters.
One common theme is the corruption of the hero system. These fanfics often show Deku turning into a villain because he sees the flaws in how heroes operate. Another theme is the exploration of good and evil. It makes readers think about whether Deku is truly evil or if he has valid reasons for his actions.