Even Nidhogg's own father pretty much deems him a lost cause that has gone completely off the deep end.

(Mind you, as a side note, I'm not of the opinion that Hraesvelgr is morally any better than Nidhogg, but at least Hraesvelgr didn't want to continue the conflict after Nidhogg was slain. He just didn't want to end it either, the feathered arse.)