He might offer her a warm drink like tea. Tea can have a soothing effect and help with cramps.
In many fanfictions, Harry might comfort Hermione by simply being there for her. He could sit quietly beside her while she's upset, offering his silent support. Maybe he'll hold her hand gently to let her know she's not alone.
One memorable moment could be when Harry first realizes Hermione is on her period and his immediate concern and gentle approach towards her.
He might offer her a warm drink like tea. In many fanfictions, Ron is shown to be quite caring. He could bring her a blanket to make her feel cozy and just sit with her, listening to her if she wants to talk about how she's feeling.
Another way Snape could comfort Harry is by standing up for him in certain situations. Maybe when other teachers or students are being unfair to Harry, Snape steps in and defends him. This act of protection can be a great source of comfort for Harry, as it shows that someone is on his side even if they have had a rocky relationship in the past.
One specific moment could be when Hermione is stressed about a big project for school. Harry might bring her a cup of tea and sit with her while she works, just being a calming presence. He could say things like 'Hermione, you're the smartest witch I know, you'll do great on this' to boost her confidence.
Well, in some fanfictions, Harry might comfort Tonks by simply being there for her. He could listen to her problems, like if she's worried about her family or the situation in the wizarding world. Just his presence can be a source of comfort.
In this fanfiction, Harry could comfort Ginny through his words. He might tell her that what happened in the Chamber was not her fault. He could share his own experiences of facing difficult situations and how he overcame them, making Ginny feel that she too can get through this tough time. For example, he could say something like 'I've been through a lot of scary things too, Ginny, and we've always come out stronger in the end.'
Harry could comfort Hermione by giving her a small gift at the Yule Ball. It could be something he made himself, like a simple charmed flower that never wilts. This would show Hermione that he values her and wants to make her feel special. She would be touched by this gesture and it would help her forget about any negative feelings she had.
Well, he could use his magic skills. Maybe he casts a powerful spell on Ron to stop him and then takes Hermione to a safe place, like Hogwarts where there are protective enchantments.
In the fanfic 'Comfort in the Storm', Hermione is terrified during a really bad thunderstorm at Hogwarts. Harry, being the good friend he is, goes to her dormitory (with permission of course) and stays with her. He tells her stories of his adventures with Ron to distract her from the storm, and it makes Hermione feel safe and comforted.