Hagrid dies
This will be a gut check for all readers. But Hagrid is SO dead. Not only is he the one character who has the most inconsequential history, he is also the character who is the sidekick to so many other characters.
He is certainly Dumbledore's sidekick. Without Dumbledore, Hagrid wouldn't even be at Hogwarts, let alone given a teaching post.
He is a sidekick to the three kids, Harry, Ron and Hermione. Really if it wasn't for them, he would have no supporters among the students at Hogwarts.
He is Sirius Black's sidekick. Without Sirius, Hagrid wouldn't have a magical flying motorcycle to bring Harry to Dumbledore the night Harry's parents were killed.
It could be argued that Hagrid is the sidekick to Hogwarts. There was that time when Hagrid wasn't at Hogwarts during "The Order of the Phoenix" and things just weren't the same at the school. Not worse, just different.
According to my math, Hagrid will die four deaths at least. That should be some battle scene. It will probably take four death eaters to take Hagrid out, and he will probably take three of them with him. But make no mistake, Hagrid is going to die -- just like all sidekicks.