I agree with this. I too like Brook's attack, but it's neither the strongest nor his strongest.
At least in my opinion, wide-spread attacks aren't exactly the strongest of someone. Party Music + Quinte Tierce Fantasia (which are two attacks) are more crowd trimmers than inherently potent attack. So far, I believe Brooks strongest attack is Kasuriuta: Fubuki Giri ( Blizzard Slash ), where he coats his sword with his soul, bringing the freezing winds of hell onto a single quick-draw attack. It's debatable in the case of Luffy's Elephant Gun Gattling Gun, but I still think either Grizzly Magnum or Red Hawk.
I also disagree with your list on Zoro (Which, as T Bogard said, is Shishin Sonson, at least while we don't get the updated version of Ashura) and Sanji's. Hell's Memories where he makes someone suddenly combust in flames, inst his strongest attack. I'd love to say it's Mutton Shot xD, but it's most likely Poêle à Frire: Spectre, at least so far. I'm still waiting on that one single Diable Jambe empowered kick. Maybe a Diable Jambe enhanced Mutton Shot or Anti-Manner Kick Course.
I'm also unsure whether Chopper's strongest form his is Raw Strength Monster Point, thus the strongest attack would be Kokutei: Palme, or if it's the more focused Arm Point, in which I'd agree with you and choose Roseo Metel, or just the one.
I guess I just can't decide if strongest should be wide output of damage, single concentrated output of damage, or basically a finisher move.
