Hillary is already prima facie guilty of 2100 violations of the Espionage Act, and her oath of office as SecState, and her signed non-disclose about handling classified information.
The Big Deal is what the FBI-CI is finding out about who ended up with the information. Which governments got which bits out of her system, and which on-going or then-on-going US operations, technologies, sources, or methods her setup allowed to be given away to foreign spies, and how those governments used that information.
All the damage she did to the entire Intelligence Community will be hung around her neck because she was the source that allowed the cats out of the bag.
All of that is just the appetizer for what they will find at the Foundation. She had not one, but two /signed/ documented agreements with the President himself that she would disclose donors to the Foundation (1) and any apparent conflicts of interest she encountered while SecState (2).
We already now she broke both of those and repeatedly in order to sell influence, using the Foundation as a money launderer. Bill was also a go-between.
The short name for that is bribery.
And finally, the FBI has all those emails she thought she deleted. All of this leads right back to King Obama himself.
The deals with high-profile journalists to get exclusives on the pieces of this story are already being made. Pretty soon even Trump actually shooting someone isn’t going to be able to compete with the scope of this story.