On the other hand, Harry could also become more determined. He might see this as another challenge to overcome and set out to prove that he doesn't need McGonagall's support. He could start to rely more on his own instincts and the friendships he has made with Ron and Hermione, and focus on finding out why McGonagall has abandoned him.
He could become more withdrawn and start to question his own worth. After all, if McGonagall, who has been a sort of mentor, abandons him, he might think there is something seriously wrong with him. He may also start to be more distrustful of others in the wizarding community.
Harry might be initially shocked and confused. He has always seen McGonagall as a reliable figure in his life at Hogwarts, so her abandonment would be a huge blow to him.
One possible reason could be that she is under some sort of dark magic influence. Maybe a spell has been cast on her that makes her act out of character and abandon Harry.
Harry could initially be in shock. He's always counted on Hermione, so her abandonment would be a huge blow. He might feel a sense of betrayal and confusion.
She might use her magic skills to shield Harry from physical harm. For example, she could cast protective spells like a strong shield charm when Harry is in danger from dark wizards. Also, she may use her authority in Hogwarts to keep him away from those who wish to harm him, like making sure he is not alone in dangerous areas of the school.
She might react with her usual no - nonsense attitude. McGonagall is known for being strict but fair. So she would first listen carefully to Harry's problem, her eyes fixed on him, and then start to analyze the situation. She may not show much emotion on the surface, but deep down, she's concerned for Harry's well - being.
She might immediately comfort him. McGonagall is a strict but kind teacher. She could put a hand on his shoulder and say soothing words like 'There, there, Mr. Potter. It will be all right.'
McGonagall might be initially shocked. She's a strict teacher and not used to such an informal and deeply emotional form of address. But then she could feel a sense of warmth and responsibility towards Harry. She might start to show more care in her actions, like making sure he eats well in the Great Hall or checking on his studies more closely.
She might be initially cautious. Given that becoming an Animagus is a complex and dangerous process, she would likely want to ensure Harry fully understands the implications. She could start by asking him why he wants to become one.
Some might be angry, thinking he's abandoning his responsibilities. The Ministry of Magic might try to persuade him to come back or even use force if they thought it was necessary for the safety of the wizarding world. His friends, on the other hand, would likely be sad and try to understand his reasons. They might also try to convince him to return, as they know how much he means to the fight against evil in the wizarding world.
Well, it could make Harry more independent. Without Dumbledore's guidance, he has to rely on himself more. He might become more cautious as he no longer has that safety net. He could also grow to be more distrustful of authority figures since the one he trusted most has left him.
It could be that in the fanfic's plot, McGonagall has some past connection to Harry's enemies. So, her hatred towards Harry is a result of her loyalty to those she has a history with. This would create a lot of drama and conflict within the fanfic's story.