Well, in such a fanfiction, Izuku might end up in a coma. His friends would be really worried. Ochaco might constantly visit him in the hospital, hoping he wakes up soon. And Bakugo could have a change of heart, realizing he should have been nicer to Izuku all along.
He would likely feel a sense of failure. Since Izuku has such a strong drive to be a hero, being hurt by the Nomu might make him think he's not good enough yet. It could be a big blow to his self - confidence.
In a fanfiction, the Nomu could be controlled by a hidden villain who wants to break Izuku's spirit. So, the Nomu injures Izuku in a brutal way. This forces Izuku to re - evaluate his approach to heroism and his relationships with his friends and mentors. He may have to find new ways to heal and grow stronger, both physically and mentally.
They could develop a symbiotic relationship. Maybe Nomu has a power that All Might needs to defeat a greater evil, and in return, All Might helps Nomu to become more than just a mindless weapon. This would require them to trust each other, which is a unique take on their relationship considering their normal opposing natures. Also, the story could explore how their relationship changes as they face different challenges together.
A really interesting plot twist could be that Nomu was originally a human that All Might knew in the past. Maybe it was a student or a friend who was experimented on by the villains. This would create a huge emotional turmoil for All Might. He would have to deal with the fact that this once - familiar person is now a mindless (or not so mindless) Nomu. It would also add a layer of complexity to their relationship in the fanfic, as All Might would be torn between trying to save the person inside Nomu and having to fight against Nomu's actions if it's being controlled by the villains.
He would likely be more confident. Having the powers of the Human Torch gives him a new level of strength. So he might stand up straighter and be more assertive in his actions.
In many fanfictions, Izuku adapts by relying on his heroic spirit. He sees the similarities between his world and the Spider - Verse in terms of helping people. So he starts to work with the local heroes, like Peter Parker or Gwen Stacy. He learns from them about the different threats in the Spider - Verse and how to handle them. He also tries to incorporate his own fighting style from My Hero Academia with his new spider - based powers. For instance, he might combine his One For All power with his new spider - strength for more powerful attacks. This process of adaptation is really exciting to read about as it shows Izuku's growth in a new and different environment.
His friends like Ochaco could help. She might use her zero - gravity ability to assist in handling heavy parts during the construction. Also, Iida could be there to keep things organized and on schedule with his strict sense of order.
Bakugo is often a key character. In many fanfictions, Bakugo's reaction to Izuku's evolving quirk can range from envy to begrudging respect. Their relationship is always a central focus, with Bakugo either trying to outdo Izuku or having to come to terms with Izuku's newfound power.