Illidan destroyed civilizations. But for Bolvar, it should be noted Ner'zul wasn't evil before he was bound by the armor. The connection to the crown & the curse of eternal life eventually drove him mad. With Ner'zul, he had the added torture of Kiljaeden manipulating him through his dead wife, but eventually he turned his animocity toward the Burning Legion & the rest of the living.
It's not a stretch for Bolvar would eventually turn exact his rage against Alexstraza, who cursed him with eternal life. He already slaughtered dragons during Legion & now, those new runeblades are very clearly made from the bones of dragons
#1 Hype-Thread Shitposter - Overlord of the Hypethread
Bolvar totally hasn't lost some of his sanity/humanity, no way definitely not.
Still loved the expansion. But any forward progression will result in people complaining when it doesn't line up with every single one of their expectations.
Bolvar is a good guy: that's the "hook" of this expansion, us working with a Good Lich King. Look at the key art where the sun is shining on him.
The cinematic has a huge chance of him kicking Sylvanas's ass and maybe killing some Valkyr. That wouldn't happen if he was the new baddie.
The world revamp dream will never die!