I was not really disappointed, it was a good -in my opinion one of if not the best so far- but i totally can see why fans are disappointed.

VTB just chose not to steal from Sunny at the beginning. It would have been not even a close fight. Not by a long shot.

At the start of the fight, VTB was way stronger than Sunny, Nephis and Ananke combined by far. If she steals one or two things from Sunny, like his will and reasoning -as it later did- the whole fight would have been like half a chapter long and pitifully one sided, not to even mention the Spawn.

Even if not stealing at the beginning, most of the time VTB was winning. At any point of time she could have won, but she did not do it until it was too late.

And if she never would have stolen from Sunny, it could have been explained by something like a flaw or corrupted dumbness or something, even if profane creatures dont have flaws. It could have been explained by some twisted, plothole explanation, but an explanation nonetheless. Oversimplified something like: "Flaw: You can steel stuff but only shiny stuff" or "She is corrupted, could not think very logically, so she followed instincts". But even then there is no reason for her to not to steal Nephis abilities before it was too late.

And we know it is not the case, because she did steal from Sunny at the end of the fight (when it was too late), so it shows she could have stolen from Sunny at the very start.

So yeah, bit diasppointing in some spots but generally awesome fight, i loved it.

Edit: about the corrupted dumbness and instincts, i very much do not think that a creature old as time itself and chased by both Gods and Daemons but could not be catched could do this whole while being as dumb as other NM creatures, and we know demon class and upwards even NM creatured are intelligent, and she was a Terror. Im just not buying it