Considering that we were much weaker in d1 and still beat Oryx 2x in his throne world, meanwhile Nezarec was only killed by Savathun after she tricked him, and when we fought him he was probably only at 1% of his original strength. I'd say Nezarec would probably win. Also consider that Nezarec acquired his strength and power on his own and was very powerful before he joined the Witness while Oryx gained all his powers from the Witness.