The remaining WB pirates could take out WB imo aside from their emotional barriers ofc. Marco, Jozou and the Rose swordsman guy are admiral level or there about. Marco I believe is not that powerful haki-wise since he can rely on his fruit anyway so I don't know how damaging he could be to WB. But basically I don't think that comment about BB is a big deal.
Why do you have Akainu so high? What'd he do lately? All he's done is narrowly defeat Aokiji. No?
Imo top 5 based on current feats and comments in no particular order:
Shanks (Yonkou and with a small crew at Marineford made the Marines stand down so must be pretty strong)
Kaidou (Yonkou)
Mihawk (stronger than Rayleigh)
Blackbeard (mofo hurt Shanks, beat Ace easily and has shown some other physical strength feats)
Big Mom or Dragon (both got crew hype and influence hype but not much clear fighting power hype)
How I think it is really:
Shanks
Mihawk
Dragon
Kaidou
Blackbeard
No Big Mom because like her name implies I think she just controls her crew through respect/patronagr rather than being all that strong herself. Think her crew is top 5 (along with the other Yonkou and The Revolutionary Army, although idk if they're really pirates in the same sense) but not her herself.
Sengoku could still be in there. Idk, seemed pretty strong. His job isn't to fight which would explain him not fighting at Marineford.