Harry might react with defiance. He has always been a brave character, so he could look Snape straight in the eye and not show any fear, even though he is in a vulnerable position.
Another possibility is that Harry retaliates physically. Given his Gryffindor courage and his history of standing up to bullies, he might push Snape back or try to break free from his grip. This could then lead to a more intense confrontation between the two, which could further the plot of the fanfiction.
Maybe Snape suspects Harry of being involved in some sort of dangerous activity related to the Dark Arts. Pressing him to the wall could be a way to force Harry to come clean about his actions or any knowledge he might have. It could also be that Snape is acting out of his own insecurities and pent - up emotions towards Harry, which he has been suppressing for a long time.
Snape could initially be skeptical. Given their long - standing enmity, he might not believe that Harry's apology is sincere at first. He might respond with a cold glare or a sarcastic comment, like 'Potter, your apologies are as empty as your head.'
Harry might be shocked at first. After all, being hit by a teacher, especially Snape, is unexpected. He could immediately get angry and want to retaliate, but hold himself back because of the situation.
Harry might initially be shocked and angry. He would probably struggle against the restraints and demand to know why Snape is doing this. He could yell at Snape, asking for an explanation and protesting his innocence if he believes he has done nothing wrong.
However, as the story progresses, Harry may start to understand the reasons behind Snape's actions. He could become more resigned and accept the punishment as a part of his growth. He might use the experience to become more cautious in his actions and more respectful of the rules.
He may also get angry. Harry has a strong sense of justice and self - worth. Snape's rejection could be seen as unfair in his eyes, especially if he has started to develop some sort of positive feelings towards Snape. So, he might lash out at Snape or even try to prove him wrong by becoming more independent and successful on his own.
Harry might be initially shocked and embarrassed. A Howler is a very public form of scolding, and in front of all his friends and classmates, it would be a humiliating experience for him.
He would probably be in shock. Snape has spent so much time around Harry in one way or another throughout his years at Hogwarts. His immediate reaction could be disbelief. He might stand there frozen for a moment, unable to process what he's seeing. Then, the full weight of the situation would hit him, and he could break down in a rare display of raw emotion.
He might be extremely shocked. Snape has his own views on the Malfoy family and Harry Potter. Given his complex relationship with both, he could initially be in disbelief and then perhaps a bit angry that Harry would be a fan of a Malfoy.
Snape could be in shock. He might freeze for a moment, unable to believe what is happening. His face would show a mixture of horror and disbelief as he holds Harry's dying body.