Theoretically we could start posturing the cardpool towards the ultimate champion by systematically removing their answers. Who will come out on top? True Name Nemesis? Emrakul? Progenitus? Brushwagg?
Also they're the same color. If you're so deep into black that you're casting a BBBB spell, presumably others at the table will have less equity in black.
What about a red creature that enters with a +1/+1, but you can remove a +1/+1 counter from it to exile the top card of your library and play it til end of turn.
I will say, as much as I'm not super a fan of Upheaval / Armageddon, these cards have led to some super interesting games over the years. When you cast one of these big spells and the game doesn't end immediately, things can get juicy.