No he didn't... Just sent him packing. Pretty sure you can't kill a Daedric Prince. Anywho, my Nerevarine was pretty damn powerful. I doubt the Dragonborn could take him.
im willing to bet most of that power wasnt legit.
anyway, this question is hard to answer because we dont quite know how powerful the villains are, since most of them are just so pathetically easy in the games, apparently that is no longer the case in skyrim, since so many things can insta-kill you early on, and still beat your ass at later levels,
i mean, reading the elder scrolls novels... i read about things that made me feel like i was reading a dragonball z novel.
the characters' powers were off the charts, it seemed...
people seem to forget... the dovahkiin has access to powers and abilities that the past characters didnt, so no matter how powerful your nerevarine or champion was... the dovahkiin will always be stronger.
ok, take out the game restrictions, i would imagine the dovahkiin would slow time, use elemental fury and chop the nerevarine to bits and pieces... and if he needed to, could even use that ethereal power to avoid any and all damage thrown at him.
the dovahkiin has invincibility, super speed, the ability to slow time, summon storms and lightning to blast you to dust, call for aid from nature's creatures, as well as a powerful dragon ally.
sorry, defend your nerevarine all you want, but the dovahkiin would definitely crush him/her.