Immortality Negation
Anos resists immortality negation (types 3, 4, and 8) because he can survive the destruction of his source, which grants him that immortality. The only problem is, destroying the source isn't immortality negation; It's just how reliant immortality works in this case, where
characters rely on their sources. So there's no "immortality negation" to speak of here; That'd be like saying Harry Potter has immortality negation from destroying Voldemort's horcruxes. The same logic applies to Anos' own immortality negation through Venuzdonoa, though in both cases it seems like HGR negation is fine to stay.