One of Jason's brutalities is his X-ray brutality and yeah it can only be done by sweep distance or further because he has to walk for it to work. So far the known brutalities with an X-ray is Jason and Sonya. They may add some more as DLC in the future.

At what levels do you unlock new Faction Kills?

already added faction kill requirements,also,added Jason's brutalities,and Kenshi's hidden brutality.

Added the Outworld Marketplace stage brutality(both versions)

So I just saw Mustard do Sonya's brutality with imposter Shinnok. Awesome! I wonder if that is the only one or if there are others he can do. Here is the link if anyone is interested, it is at about 8:15:

https://www.youtube.com/watch?v=S8Ckf5wiI7Y