Originally posted by The_Tempest
YouTube video8:07-8:30. You can see him charge the cannon. Setting that aside, I'm not sure why we would assume a Nebulon-B frigate can oneshot a Star Destroyer.
Because the Salvation is armed with a prototype Fusion Accelerator Cannon, which has never been seen before or since, so the power of it is unknown and might well be enough to do that.
And we don't see him charge it. We see him lightning the 2 blue things until they then lightning the sorrounding blue things independant of him and then he charges up a Force Push to fire the cannon. That could easily just be him turning it back on.