Re: I know who the villain is.
While I'm positive it's not Soran, it's not a far fetched idea. Soran did initially make it into the Nexus, maybe he still has a bitter "shadow" there. It was shown that you can pop in and out of the Nexus anywhere along the timeline, maybe he went back to his younger self in the new timeline to convince him to seek revenge on Kirk and company. He's established as a nutty obsessive, so he just goes nuts at a younger age.
P.S. I agree with the earlier poster that Soran was a decent villain, and not least because it was Malcom F*****g McDowell
"Enterprise, starship, the places you've been to, the things that you've shown us, the stories you tell, Enterprise, starship we sing to your spirit and the beings that have served you so long and so well"