He let him in.
"In Secret Wars 1, I am aware.
However at other times Thanos has outright invaded G Man's mind and struggled with him there. "
Rachael under her own power can't hurt Galactus.
"Funny he never does this in his fights, like when he's getting hurt by Rachael Summers. "
And I recall an instance in particular that the Invisible Woman finds her attacks going through Galactus without harming him.
Then there is the instance above where Galactus displays his multidimensional cookie layer where you have Thor and friends blasting away unable to touch him.
"G Man could shrug off universe busting? I don't think so"
He already did it before he was Galactus, he will manage. Regardless Broly goes down long before that happens.
I'm suprised no one mentioned the one time Morg unleased the nullifier on Tyrant and Galactus who we see later survived.
"G Man is quite capable of dieing"
Not really, the whole process of killing Galactus is a tricky task.
The closest thing to dead you've seen him is being a star that would burn for eternity, which only took a reality warper and his sister to remake him good as new, ergo he didn't enter Death's realm despite being dead.
Heck Death itself has shown an interest in keeping Galactus alive, then theres the instance when the inbetweener blasted him, his ship, and company to pieces just to reform in a plit second everyone there.
"and the SS has remarked that his death would cause an explosion 42 light years wide."
His first "Death" released a being that was going to destroy the multiverse if Frankling Richards and Valeria hadn't revived him, in which he makes a damn fool of Abraxas.
The closest other instances where from starvation and Annihilus planning to turn him into a bomb using Galactus's own power, to destroy the universe and then some.
Galactus is big on not wanting to kill despite ending civilizations, perhaps the 42 lightyear boom is him containing the damage as best he can?
Although what happens when Broly dies? A couple of bad sequel films?
I guess Broly isn't capable of tanking galaxy busters either if he doesn't die and instantly destroy galaxies.
Your trying to use something that means absolutely nothing to a character's power as a means to lowball them, what happens when most things die in fiction despite being powerful beings?
Nothing, Goku has kicked the bucket plenty of times and he was the most powerful being in his universe, it was still there.
" In other instances his power was trying to be harnessed in order to destroy the universe. "
Not harnessed, just setting the fuse to a being that is already a walking universe himself, who regularly has gone up against being and even nearly devoured Mephisto's pocket dimension.
It was already proven in DBZ that being more powerful will do nothing against matter manipulation, as evidenced by Mystic Buu turning Vegito into an elastic candy,
Your comparing two completely different things.
"Vegeto let that happen, when he put up a ki barrier, magic absorption failed. "
Vegeto tanked a direct hit from the candy beam and was turned into a snack, Buu tried to absorb him and he placed a barrier and still found himself shrunk.
Ki Barriers don't have feats that give them ANY sort of protection against any time of matter manipulation, magic or straight up abstract reality warping from a guy in a big pump suit.
If anything that showing directly supports that Ki barriers do not provide complete shielding against the magic Buu provides, thats all.
That doesn't make any sense.
"With Broly's infinite energy, he could put on a indefinite ki barrier. (of universal magnitude) "