Comments that only explain a certain point don't mean much. We really need a blog for this, but I don't have time to do that right now.
So for now I'll just explain the logic of scaling.
Current Cosmology
Cardinal World
An hypertimeline [Low 1-C], contains the Cardinal World's Universe and an infinite number of alternate timelines [2-A] of the Universe and the insignificant 5D structure between timelines.
It is essentially the Low 1-C construct that Ivaraj, the World Destroying Dragon, failed to destroy, which continued to exist even after the Cardinal World's Universe was destroyed by Feldway.
Cardinal World's Universe
It is the main universe that was destroyed by Feldway through an unknown ways.
Cardinal Universe's Main Planet
The planet that contain the power of Veldanava (Creater of Countless Worlds), who cannot be destroyed even by Milim, probably the most powerful person after Feldway.
Note: Even a
Tower with Veldanava's relic can block the attack of Michael, one of the strongest characters in the series.
Dimensions
They are containers [with own timeline] that can even contain
Dimensional Worlds [Low 1-C] such as Cardinal Worlds.
These Dimensional Worlds both contain
Parallel Universes (like Cardinal World's Universe timelines, remember that essentially the
MWI applies to every plane of existence) like the one Velgrynd travels through and are home to
Galactic civilizations.
Isolated Dimensions
They are essentially isolated states of the dimensions that contain the worlds. They can contain a simple dungeon to a
sky full of stars.
The Ramiris Labyrinth consists of isolated dimensions, and these dimensions and other Dimensional Worlds are separated by
space-time.
Scaling
Now let's evaluate the feats of the characters.
Carrera's Abyss Annihilation statements:
A black hole capable of destroying a planet, and Kondou predicts this magic could destroy the dimension Velgrynd created, but since the properties of the dimension Velgrynd created are unknown, we do not assume that this feat is Low 1-C.
Note: Here, the term "planet" is like a planet used when giving an example, does not refer to the Cardinal Universe's planet.
Velgrynd's feat in destroying 50 floors with one strike (also Veldora's 2-3 floors feat) the of the Ramiris Labyrinth:
Apart from the fact that each floor in the Ramiris Labyrinth is an isolated dimension, they have their own timelines and can even contain the starry sky, we don't know much about the structure of the floors, so we do not assume this feats as Low 1-C.
Zalario's destroyed dimensions feat:
Dimensions destroyed by Zalario; includes Worlds that appear to have the same cosmological structure as the Cardinal World, with parallel universes and galactic civilizations, so we consider this feat a Low 1-C.
"True Dragon's can blows up the weak/small worlds" statement:
Here again, the Worlds mentioned are Low 1-C structures where MWI is valid during travel to the past in alternate dimensions.
As far as I remember, the expression weak rather than small was used here, but even if the kanji really meant that these Worlds were small, it could not be said that the World in question was the size of a planet or solar system based on this word alone.
WoG Support:
――ヴェルグリンドには空間移動能力があります。並列空間にも移動できますが、その力で他の世界に影響を与えたりすることはあるんですか?
伏瀬厳密に言えばあります。でも一応制御はしてるので、影響を出さないようにしていると思います。それこそヴェルザードだったら、そんなの気にしないでしょうね。相手の世界が壊れようが関係なしと思う可能性が高い。このふたりの間には、気配りができる人とできない人の明確な違いがありますね。
Fuse confirms that Velgrynd's power can affect parallel spaces (which seem to be parallel universes in this context) and even other Worlds, and states that she can destroy them, but does not allow to do so.
――リムルを中心に描かれている物語だからこそ、激しい戦いがあっても温かく見えるけど、その外側の世界は厳しいという温度差。改めて、「転スラ」はリムルの物語なんだな、と思います。
伏瀬そうですね。ギィなんかはひとりで世界を滅ぼせるけど、しないんですよ。なぜなら、それに意味がないから。意味がないことをするキャラがあまり出てこないのが「転スラ」だと思っています。
In the same interview, Fuse stated that Guy Crimson could destroy the World by single.
Note: Fuse is referring to the Cardinal World here, but later wrote a story where even Satanael Milim couldn't destroy the Cardinal Planet, and even Feldway could only destroy the Cardinal Universe, and even Ivaraj, the Dragon who destroys worlds, couldn't destroy the Cardinal World. So this can only be used as a supporting.
Additionally, Velgrynd can easily destroy a starry sky with a single hit, while a solar system level attack is nothing to her.
In conclusion, I disagree.