But your only counter has been saying "Yeah but the same is said for Sentry".
When it isn't, because as Ive been saying in these instances we look at contradictions. In your example we know that a decently powered Galactus is far above Sentry, so we can logically assume that either it was a weakened version or something else intervened.
While in this one, we know that Barns is correct as he was the one attacking the beast in the first place. His fear alone shows how formidable they are against him.
If you threw a bomb as it downed one, but later another brought it back. Would you be scared and remark how strong they are? No, of course not, you just downed the beast,