Awesome Music: The Voice of Steel, in spades. Verity isn't a slouch either, nor is their side of The Spirit Never Dies.
The music pre-Voice of Steel has its fans despite the lyrical themes, most notably Lunar Poetry and Goat Horns.
It should be noted that Lunar Poetry and Goat Horns (and Twilightfall and To the Gates of Blasphemous Fire) are actually from before the band openly embraced NSBM, mostly being anti-Christian than anything else. The lyrics from the band's earliest albums are actually lost to the mists of time, apart from "Perun's Celestial Silver" and "Kolyada", plus the lines that can be deciphered by ear. (If the lyrics to To the Gates of Blasphemous Fire have political themes, meanwhile, they're oblique at best.) When other bands covered the early songs for 22 Years Among the Sheep, many of them wound up having to write new lyrics.
The live album Kolovorot also deserves some mention for containing two hours of well-recorded, faithful live renditions of the band's complex material, many of which (particularly the Nechrist tracks) sound better than the studio recordings. And if you want their stuff on vinyl, you'll have much better luck tracking that down for a reasonable price than you will The Voice of Steel — and every Voice of Steel track except "By the Path of the Sun" is on there.
Audience-Alienating Premise: It's telling that newcomers introduced through Voice of Steel or Verity will be a bit unsettled if not borderline uncomfortable at the band's embrace of anti-Semetism during the Nechrist through Weltanschauung era.
Broken Base: Without...going into details, there are those who prefer the old material versus from Voice of Steel onwards. Or whether or not it's a good idea to put aside the implications of the later lyrics.
Whether or not one should listen to either version of Weltanschauung despite both being the same aside from minor differences. The main difference apart from the language is the connecting instrumentals, which apart from "Endless Vast Swamps" are actually completely different songs despite the names meaning the same thing in different languages.
Even beyond the lyrics, Nechrist is also a source of contention for the murky production and strange guitar tone, which is particularly inexplicable given how pristine the production on their earlier material had been. It's as if Emperor had gone from the sound of Anthems to the Welkin at Dusk on their second album to the sound of their demos on their third. The Nechrist songs on their live album Kolovorot seem to be better liked overall because you can actually hear the melodies clearly.
Heartwarming Moments: Yes, believe it or not, even this band has one. Komu Vnyz' member Serhiy Stepanenko had fallen unexpectedly ill and required a kidney transplant, so Nokturnal Mortum released their cover of "Lira" (which they'd already recorded) as a single in advance of the release of Verity in order to raise money for him.
Never Live It Down: Their early (well middle) NSBM days, to the point where people are unsure if the band is regretful of their time doing NSBM music due to still performing at far-right wing festivals.
