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.'
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 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.
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.
Perhaps when Harry is wrongly accused of something, and McGonagall uses her influence and knowledge to prove his innocence. She stands up for him in front of the whole school or the wizarding authorities, which is a very significant moment of her protecting Harry.
Well, initially McGonagall adopts Hermione out of a sense of duty and seeing Hermione's need for a more stable environment. In the beginning, Hermione is a bit in awe of McGonagall. But as they live together, they start to have small moments of connection. For example, over a shared cup of tea while discussing a difficult spell. Slowly, they start to understand each other's quirks. McGonagall learns about Hermione's passion for knowledge and Hermione discovers McGonagall's softer side. Their relationship blossoms into a beautiful and deep bond that affects both of their lives positively at Hogwarts and beyond.
Some characters in the harem might be developed as admirers of McGonagall's strict yet fair teaching style. They could be shown as constantly trying to impress her with their magical skills, like a young wizard who practices transfiguration just to get her attention.
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.
One common plotline is McGonagall protecting Harry from the Ministry of Magic when they wrongly suspect him of something. For instance, if the Ministry believes Harry is using Dark Magic, McGonagall stands up for him, using her influence and knowledge of Harry's character to prove his innocence.