Superman probably wins if he decides to end it as fast as possible. Otherwise Nimrod analyzes his weaknesses and takes him down by replicating red sun emission spectrum.
Superman 7/10.
(Note: kryptonite radiation might take some time for Nimrod to synthesize but the spectrum of a red sun is well-known and easy to reproduce for someone like Nimrod.)
This is basically a fight against the clock for Supes. Nimrod is a weakness-exploiter and Superman has some of the most notorious weaknesses of all herald+ level characters.
And it is not easy to put Nimrod down, either. Rogue once absorbed the powers of the X-men; teleported Nimrod's arm off and then smashed him to bits with the combined powers of Colossus and Ms. Marvel.. and Nimrod immediately repaired himself the next panel.