if they are on a battlefield (of some sort), then Galactus can annihilate them with sheer power output. that's just a simple, completely effective method.
then there's simply consuming them - Galactus can consume realms and has already once consumed the Elder Gods, these guys will be easy fodder.
then there's siphoning off their energies... he's done it to planets, to Ceira, he has no limits (as demonstrated by BCA)... reducing them to nothing.
then there's conversion, he could easily transform and mindwipe Thanos into a herald, then do the same to the others.
there's so many ways that Galactus would decimate them... this is just Batman prepping against Thanos.
No, all of these attacks require the opponents to stand around in dramatic pause and wait. This is not going to happen with this lot. They have the brains, tech, and resources to ensure that none of these attacks will be effective.
Blasting, Not going to happen
Mind wipe; a twelth level intellect, Thanos, one of the most powerful Gods around, and Loki simultaneously ??? I don't think so.