BC : Illidan = wants to create an army against the Legion, uses underhanded/ morally bad tactics, Kil'jaden = is part of the Legion, simply doing his master's bidding
Wrath : Lich King = wants to unify azeroth as scourge to resist the Legion/ external threats
Cata : Deathwing = wants to destroy azeroth and her people's for the Old Gods
MoP : Garrosh = wants to destroy the alliance/ most of the Horde to establish his true horde and rule the world his way
WoD : Grommash = wants to create an orcish army to conquer countless worlds, Archimonde = same as Kil'jaden
Legion : Gul'dan = wants to bring sargeras to azeroth, Sargeras = wants to create one uniform force against the void lords
BFA : Sylvanas = wants to kill as many as she can, Azshara = we don't know her full plans yet, but she wanted to get out from N'zoths grip, N'zoth = Old God shit
So, turns out villains don't just want to destroy the world