Sanji fazed S-Shark but the chapter kinda made clear doing actual damage, significant damage isn't easy whilst the flame is on. He pretty much left the most noticeable impact on a Seraphim since not only was he stunned but was hurled into the lab followed by the explosion but that's not really damaging the Seraphim within the context of the chapter.
It's pretty important considering Zoro drew blood from King but it was later regarded as not enough and even Shishison had King fazed but was to no avail. Sanji will get his feats against S-Shark, his eyebrows switched after the opening attacks and he hurled the guy and sent him stunned and white-eyed. Now the real action is about to begin, eyebrow-switched Sanji against S-Shark 1v1. It's gonna be good.
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Honestly, S-Shark in speed-mode needs to bist out something amazing cause speed is Sanji's game at this point whilst S-Shark hasn't reacted the best against Sanji's speed. There are no distractions from here on out so we'll see how S-Shark and Sanji handle each other's abilities. Going into it, it seems like a favourable match-up once Sanji gets him to swap modes.