What about max mercury? And the obvious squirrel girl lol
Doubtful. Recently, during Fraction's run of Thor, we see Thor actually hurting an otherwise occupied Galactus. However, this appears to be out of harmony with what has been said about the massic cosmic entities/abstracts, such as Galactus, Eternity, etc. Beings like Galactus appear to be more energy in nature. What we see (and what everyone else in comic land apparently sees) is an anthropomorphic image...a physical manifestation...so that lesser 3 dimensional beings can grasp what they are looking at:
Above, from Quasar 37, this is explained to Quasar. Below, we see something similar from Silver Surfer 10, volume 2:
Galactus' being hurt by Thor (during Fraction's run) is never really explained...no offense, but I don't think Fraction ever really had a grasp on Galactus (or Thor for that matter). Whether harming Galactus' "manifestation" is a result of some sort of psychosomatic offshoot resulting from his telepathic skirmish with Odin (my best guess....) is never really elaborated upon.
At any rate, for my part, I'm doubtful Wally West could seriously do anything to a character on that level.