Actually the WORST moment in Galactus' history was when he was being stalemated by Quasar (I don't know what issue that was in but the scan was posted on these boards). Now that's absolutely humiliating. Or the time Thanos blasted him off his feat and miles across a moon or something, meanwhile Thanos was unable to even budge Odin.
But regarding Galactus vs Tyrant (any version) in their final encounter, no one and nothing could have saved Galactus from Tyrant except the UN.
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..even the outer hells are indifferent matters for they bow only to potent and archaic Nodens.