so it said on a bio written years ago....... in his last couple of showings nothing has hurt him without first specifically draining his ionic energy
and MM can't maintain Superman style strength according to this
http://www.starnet-database.com/dbase_deo/profiles/mmanhunter/manhunter.html
"At a rest state, the Manhunter can lift approximately 20 tons. Given a few minutes to reconfigure, he could match Superman pound for pound for about a minute. Then the bio-polymer would begin to suffer under the strain and begin to unravel. While the Manhunter's strength can be on par with Superman and he lacks the long term endurance and stamina of the Kryptonian."
MM would get crushed in this physically - CN has beat down thor and wonderman simultaneously and more recently he handled all the avengers and T-bolts at once including wondy, atlas and iron man. vision's intangibility did nothing either - CN was too supercharged in their first meeting. all of the JLA would be a good contest against CN, just like it was a great abttle when he took on all the avengers and the t-bolts.
problem - no one knows what defenses CN has against telepathic powers. MM might be able to take him this way. not sure.