Perhaps Tonks starts dating someone else, like Remus Lupin. Harry has some unspoken feelings for Tonks, and seeing her with Lupin makes him feel heartbroken. In the fanfiction, it could show Harry's internal struggle to accept the situation and his pain at seeing the woman he cares about with another man.
Another possible antagonist could be the Ministry of Magic. If they suspect Harry of something and force Tonks to spy on him or cut ties with him, it would break Harry's heart. The Ministry's strict rules and paranoia could be the driving force behind Tonks' actions that lead to Harry's heartbreak.
Perhaps they are characters in a modern - day wizarding world where they are both part of a secret magic society. Edward could be a powerful wizard from an old family who feels threatened by Harry's new - found powers. So, he decides to break Harry's heart to assert his dominance.
One possible plot could be that Snape reveals some long - held secret about Harry's parents in a very cruel way. For example, he might tell Harry that his father was not as heroic as he thought, and this shatters Harry's idealized view of his family, thus breaking his heart.
Well, it could be that Edward, perhaps jealous of Harry's popularity or a girl he likes, spreads false rumors about Harry. This causes Harry to be ostracized and his heart to break as he loses friends and respect.
Yes, in some fanfictions, Tonks could potentially be written as Harry's pet. Fanfiction allows for a great deal of creative liberty, so authors can come up with all sorts of unique relationships between characters.
Draco might become withdrawn. He could isolate himself from his friends and spend more time alone in the Slytherin common room, brooding over what Harry has done to him.
One possible reason could be a misunderstanding. Maybe Harry misinterprets Draco's actions or words in a way that makes him do something that breaks Draco's heart. For example, if Draco is secretly trying to help Harry but Harry thinks he has some malicious intent and publicly shames him.
The relationship would become extremely strained. Harry would likely go from having some level of respect or at least tolerance for Snape to feeling intense hatred. He might avoid Snape at all costs and even start to plot revenge in his head.
Well, her possessiveness might isolate Harry in a way. He may feel smothered by her actions, which could cause him to rebel or try to distance himself. This creates a new dynamic in the story where Harry's actions are influenced by trying to break free from Tonks' possessive hold, and this can lead to all sorts of plot developments like him making unwise decisions on his own or seeking out other allies who are more understanding.