And Thanos' father and brother, as well. Depending upon how the big guy is used it could be looked back upon as a foundational book in the Thanos-related mythos. He has the chance to be the bronze age's transcendent villain key, as Action 23 is to Gold and FF 5 is to silver. Tougher with villains, but it happens. JIM85 also has moved in that direction; will be interesting to see if it can keep up.
Problem with villain keys is half the ones with Luthor/Dr Doom-level potential appear first in books that would be keys anyway, though I argue they add to the significance greatly -- referring to Joker and Catwoman in Batman 1 and Magneto in X-Men 1.