It's not that Welt has the same power he had as a Herrscher(power or Reason) because he blatantly doesn't. It's that his new powers as a Pathsriders + Star of Eden make comparable if not stronger than his prime. Regardless if you consider the Star of Eden "Welt's power" is beside the point here. Even if Zepyhro and Welt are equal hax wise (defintely not stat wise). That has 0 bearing on Acheron......she can access the power of her ENTIRE Path. She has survived being consumed from a manifestion of IX before becoming and Emanator and resisted being conceptual erased from existence whenever she goes to the Horizon of Existence. If you believe Star of Eden is comparable to the Nihility then you are either grossily misinfoirmed on what each do or are delulu. I can't even really see why Star of Eden would even affect Acheron.
That girl can erase events from history so thoroughly that THE REMEMBERANCE doesn't even know they occured. That's what she's packing. No offense to Welt but the only character we know that can potentailly hang with Acheron is amppped Phainon while he burns through his existence (even then it's likely Acheron can do something similar through tainting her existence with Nihility).
To address Acheron's blade to balck hole comparison, this is irrevelent to argument becuse much like Welt....Acheron is deliberately hiding her identity and powers at this point of the story. She is downplaying herself and minimzing her involvement by aruging Welt is more dangerous because of Star of Eden. However the danger she possess has very little to do with her sword and moreso the her effects on all of existence as draws all things closer to Nihility by merely existing. We are talking about the same person ELLIO CAN'T SEE THE FUTRUE OF BECAUSE NIHILITY ERASED IT. She has no past nor future making her acausal. She can stop time, freeze space, cut trhough fate itself, travel through higher dimensions (like all Emanators), BFR you to the Horizon of Existence (which is an instant win-con), manipulate causality, erase anyone or anything from history, and even affect the power of several Paths themsleves.
I'm not a Acheron stan, I love Welt and like him more as a character but it doesn't make sense to say he's stronger than Acheron. Let's look at it narratively, if Welt is equal to Zephyro whom you think is stronger than Acheron (because you think she doesn't have galaxy level scaling even though everyone in the game does with simple logic and Emanators 12-D/Hyperversal) THEN is Phantiliya's adundance clone stronger than Zephyro? Is Dominicus also stronger than Zepyhro? Welt has fought with us against eneimes in which we desperately needed to win or everyone was ****** yet we always required outside help and a combined effort to simply stand a chance. What you proposing either makes Welt a giantic asshole or incompetent. Neither are the case.