To be fair, Nami and Zeus only probably do 1-5% of beating Ulti while BM did 95%.
Maser Canon was lethal asf and probably stronger then the most G4 attacks, Ulti standing up after such a attack was already a surprise.
But yeah I was hoping for a battle battle where Nami combinate Zeus with her own moveset to make op attacks
I don't think a fight was even possible there. Oda had already shown that a single Ulti attack was enough to neutralize Nami. Even after the powerup, nothing has changed in this regard. Oda picked up opponents they did not fit and then twisted as best he could, so that Mugiwara's "beat" at least someone famous.
And it was the deadly wounded, basic Ulti(without Haki and DF). In general, it's funny how Oda presented the" whole " fight(I mean, starting from the very beginning of the chase).
Usopp's skull was broken, and in the last chapter he was attacked again on the skull, but he suffered relatively easily. Oda, when he confronts the protagonist with antagonists who are much stronger than the first, the protagonists gain infinite stamina and quickly recover. Or avoid taking damage altogether with some plot twist. That's why it's so hard to accept such a shitty fight setting.