Draco may lose some of his status among his Slytherin peers. Since he was shown up in a duel, his friends might start to question his skills and look at Harry with more respect. This could lead to Draco feeling isolated and trying even harder to prove himself in other ways. He might also start to doubt his own abilities and have to reevaluate his approach to dueling and magic in general.
Draco might become more bitter and resentful towards Harry. He could start plotting some form of revenge in the fanfiction.
Well, in some fanfictions, Draco could have a change of heart. After being shown up by Harry, he might realize that his attitude towards Harry and others has been wrong. He could start to respect Harry more and even try to learn from him. However, it's also possible that he just gets angrier and more determined to best Harry the next time, which could lead to more intense confrontations between them in the future of the fanfiction.
It could be that Harry has a new spell or technique that Draco is not aware of. Maybe he got some special training from a powerful wizard. Harry could use his agility and speed to dodge Draco's attacks and then counter with a series of powerful spells. His ability to think on his feet and adapt to the situation during the duel would also play a big role in showing Draco up.
One consequence could be a huge rift among their friends. Harry's friends would surely be against this forced union and might try to rescue him. For Draco, his friends might also be divided as some may not support such a cruel act.
One possible reason could be their different values. Harry is often associated with justice and kindness, while Draco has a more complex moral standing in the original story. If in fanfiction, Draco might continue to be involved in some dark or unethical activities that Harry can't tolerate, leading to the break - up.
Often, there's the theme of power dynamics. Harry is seen as a hero, but by beating up Draco, it can show that he's not above using force when necessary. There's also the theme of friendship, as Harry might be standing up for his friends against Draco's insults.
There could also be a chance for reconciliation in the future. Maybe they both realize that they made mistakes during the break - up. Draco could change his ways a bit more and Harry could be more understanding. Fanfiction often has these kinds of arcs where characters get a second chance at their relationship after some growth and learning.
There are also some fanfictions where there is no clear winner. The duel might be interrupted, or they could end up in a draw. This can lead to a more complex relationship development between them as they both have to come to terms with the fact that neither is clearly superior in a duel.
One interesting scenario could be when they duel in a magically altered landscape, like a floating arena. The unique setting adds an extra layer of excitement to their battle.
At first, Draco might be in shock. He didn't expect Harry to break up with him at such a crucial time. Then he could try to reason with Harry, begging him to stay for the sake of their unborn child. When Harry refuses, Draco could turn to his own family for support and close himself off from the outside world for a while.
Well, one consequence could be that Draco feels extremely guilty. He might try to make it up to Harry in various ways, like helping him with his studies secretly. In some fanfictions, this accident could also lead to a change in their relationship dynamic, from enemies to something more complex, like reluctant allies.
One consequence could be that he gains an unexpected ally in Draco. Draco might feel indebted to Harry and start to change his views towards him, which could lead to some interesting interactions between them in the future. This could also cause some tension among their respective groups of friends.