Vanilla - Kel'thuzad. Scourge, which is made by the burning legion / C'thun - Old god
TBC - Kil'jaeden
Wotlk - Lich King. Made by the Burning legion
Cataclysm - Deathwing. Servant of the Old gods
MoP - Garrosh empowered by the heart of an Old god
WoD - Archimonde
Legion - Legion controlled titan
BFA - N'zoth - Old god
SL - ???
Maybe this is the time they break the wheel no?