As long as BM's armor is down due to the photo I would say Luffy has the strength to beat her since a simple fall to her knees drew blood. If that little does that than Luffy should have more than enough to hurt her significantly.
lol that drop was just to visualize to the reader (and Luffy) that her guard was down, that means shit when it comes to her actual defense.
We'll see as for now though that's speculation, no one's ever seen her take a hit in that condition. We saw Cracker had a strong defense but once bypassed it took relatively little in comparison to other big name fights to hurt him, could turn out to be a common trait that they have good defensive abilities but not so great endurance.
Blood and scratches don't mean this much. Luffy drew lots of blood when he punched Garp, and that was nothing to him. Law drew blood and bruised Vergo's face with Counter Shock, and it didn't make a difference. Smoker did the same by punching Vergo, and Vergo completely outclassed him. The blood served as indicator that Big Mom's invulnerability had fell, nothing more.
I don't deny it could only be an indicator she's vulnerable but I don't believe that's all it was. All of those are attacks intended to do harm though not the same as simply falling and getting cut. I don't think it's that far fetched to assume that someone who had an impenetrable defense might have a lower endurance than others even being a Yonkou.
I don't really care about the notion that she might have lower endurance, I'm just saying the scratch on her knee is a shit way to back that up with because those kinds of injuries have been historically useless and aesthetic fluff in this manga.
That's a common theory. She has Armament Haki infused into her skin and when she flips out, it slips.
