And then we have these statements.
- he could easily smash the no longer needed adaptor with an overwhelming explosion of light that could turn an entire planet to dust.
- Yet that attack had held such power that it could blow away a planet
For the first one, you would need to already exceed the GBE of said planet to separate the materials constituting said planet into dust, and keep it in that form. Otherwise, the planet that was separated/turned to dust would eventually merge back together. This would defeat the purpose of said planet being turned into dust entirely in the first place.
As for the second one. To blow away a planet entirely would mean that it would already supersede the minimum GBE for that planet, as if the minimum amount of GBE were to be applied directly to that specific planet, said planet woud slowly drift apart away from its previous position/state (instead of you know, being blown away).
"Also "Turning a planet to dust" can very easily be a metaphorical or poetic phrasing."
Or you could just take the statement at face value, considering that this description is more concrete than something like "shaking the stars themselves" or assuming that an entire galaxy has been destroyed despite the Suns and planets in said galaxy still remaining intact.
Anyways, I don't see a statement that Fiamma (or any 5-B) feat can only "just destroy the world", when it specifically mentions that planets are either blown away, or destroyed completely.
Agreed with Lazyhunter and DontTalk for the evaluation of this feat.