The only thing that is immediately affected by the Grand Star being is the small star Bowser ends up on after beaten by Mario (Which off topic how tf did he even end up there he was knocked into the main small star he fought Mario on), everything else remains perfectly stable it's only that specific star exploding and becoming a black hole. I can see maybe all those distant stars being dragged into black hole which can net nice results but it's hard to tell given the effect for the black hole appearing is just it fading into view in front of the background.
That “small star” isn’t isolated — the entire region is a composite structure suspended in space by Grand Star energy.
The cutscene begins with the Grand Star pulled from the machine, followed by the entire construct beginning to warp and distort. Rosalina’s narration outright states that “the universe will collapse” as a consequence, not “a single star.”
The event is not localized. The black hole visibly pulls in the light of the skybox, and Peach’s Castle — which was taken from another world — is caught in the gravitational wave.
Is his construct ever said or implied to be galaxy sized? Is there also any iidication that the Grand Star recreated all those stars instead of the two of them just ending up in another location, Mario gets flung so far around from the platform near Bowser's throne that it's not even visible anymore (The platform remains completely intact when Bowser summons the black hole so it not being visible can't be from it being destroyed)
Bowsers size also isn't notable here given he's no bigger than his usual giant sizes. He doesn't have stars orbit him and if he did those would be some tiny stars given he's building sized. Unless you're referring to the white streaks in the background, which tbh I didn't notice before (I've only recently gotten a new laptop so before I was viewing the videos of the boss fight on my shitty phone lol). I think those being distant stars being dragged into it could be fine.
We don’t need explicit “galaxy-sized” text if the infrastructure serves a galactic function. Galaxy 2’s final battle takes place at the culmination of Bowser’s conquest, which involves Grand Stars, Starship Mario, and
galaxy-to-galaxy navigation.
Bowser enlarges to dwarf planetoids, and has white orbital streaks that resemble stars or fragments being pulled toward him, implying a cosmic-level event.
The Grand Star returns after the black hole collapses, implying restoration — just like Galaxy 1’s ending.
4-A isn't the immediate tier to slap onto something for things like this, cosmic scale varies heavily depending on the size of the star systems or galaxies we're dealing with it doesn't default to 4-A specifically.
That’s true — but repeatable, observable feats are what VS Battles uses for 4-A:
In Galaxy 1,
Grand Star powers a machine keeping a galaxy-scale construct (the center of the universe) from collapsing.
In Galaxy 2, Grand Star appears after Bowser’s black hole destroys his last cosmic base, restoring the region.
In both cases, the Grand Star anchors, stabilizes, and survives these events — a tiering standard accepted in other verses.
If collapse and restoration of multiple star systems or cosmic zones is depicted twice in cutscenes — and the Grand Star survives or reverses both — this is scalable energy output worthy of 4-A under standard system rules.
I don't know why you're bringing up other verses like this when nobody is disagreeing with the Grand Stars scaling to their own feats? It's just what tier it'd be specifically and how much of it Bowser can scale to when he's empowered by one that's in contention.
The comparison is not about story — it’s about VS Battles methodology.
Triforce and Chaos Emeralds receive cosmic/low multiversal tiers despite stylized, minimalistic visuals because the narrative and function indicate cosmic consequences.
In the same sense, Grand Stars are shown stabilizing galaxy-level machines and
enabling intergalactic travel — that’s repeatable narrative usage, not just headcanon.
If the same logic that applies to other minimalist visual feats applies here, consistency demands Grand Stars be treated the same under VSB's guidelines.
I'm gonna call it a night for now. Be back tomorrow.