Gaban ACOC?
I was gonna make a whole post about being torn between it but i just found the biggest indicator.
The black lightning seems very inconsistent but i can’t find a single instance where it’s appeared on a weapon before the attack without it being ACOC, tho it kinda looks weak. (Kaido/ 2nd image)
However Luffy in gear 5 doesn’t always have this coating either but the distinct lightning is enough to say its acoc (wsg/ 3rd image)
The black lightning (when it’s not acoc) comes out when a clash has occurred. Now we don’t know whether luffy blocked it (probably not). It’s also weaker, looking more like his clash with Lucci or Kizaru (last 2 images).
I’m hoping when the chapter releases it’s more obvious clear.