God's Vengeance vs the Red Entity
@Bane_of_sith: Thought the rule that bans omnipotence? I think that was more aimed at characters that cant be beat, like The Presence or The One Above All and such, the Spectre has been beaten a fair number of times.
@whydama: I will have to say no, even if Johns is pretty consistent in wanting his emotional space monsters to trump everyone (his Spectre also had trouble with Parallax in GL Rebirth...still dont get why it was latched onto Jordan for some reason during his entire tenure as the Spectre?). But honestly, I think most other writers will say the Spectre overpowers any single of these things.