I know this is not the point of your thread and that I am probably nitpicking, but I don't understand what's your definition of a "major villain". N'Zoth is not the major villain of BfA -- Or rather, he is not the only major villain of BfA, are we suddenly going to ignore all the shit that Sylvanas caused in the first half of the expansion?
C'Thun was not the major villain of Classic. Nefarian, Onyxia, and Kel'Thuzad had more of a presence than him to be honest.vanilla: Cthuun - 0
BC: Illidan - 0
Illidan was not the major villain of TBC. It was Kil'jaeden. He is the one who opened the Dark Portal through Kazzak and instigated the War in Outland. In usual Kil'jaeden style, you did not realize his deceit until the very end, when he attempted to enter Azeroth through the Sunwell. Illidan barely did anything in TBC and randomly died in the first patch (even Blizzard admitted they failed in building up Illidan as a major villain after the hype).
Again, sorry but what? Lei Shen was a minor villain in MoP. The Sha were the main villains of the first half of MoP, with Garrosh being the main villain of the second half. Archimonde wasn't the main villain of WoD, as he appeared with no build-up at all in the last 5 minutes of the story. Grommash (6.0-6.1) and Gul'dan (6.2) were the main villains of that expansion's underwhelming story.MoP: Lei-Shen - 0
WoD: Archimonde - 0
Calling him the major villain of Legion is unfair towards Gul'dan, Elisande, and Kil'jaeden, who had much more presence in the story than Sargeras during the first half of Legion. Sargeras only started being relevant in 7.3 (his previous disagreement with Kil'jaeden wasn't relevant).Legion: Sargeras - 0 (made a pathetic flailing swipe at the Vindicaar in his cinematic just to drive home the point he can't kill anyone)