Boa's ability makes her lethal to most lower-level characters, and she'd rip Sanji up, but I can't see her fruit power working on any higher-level guys like the other shibukai.
Mihawk is just deadly from what we've seen, as are Kuma and Flamingo.
Blackbeard is strong due to a hax power, But Mihawk doesn't use a fruit,and neither Kuma or Flamingo need to touch him to use their powers,so their not cancelled out...Plus Boa's Haki skills give her an edge.
When i think about it, Blackbeard is probably the least powerful shibukai...
[SPOILER - highlight to read]: That facial expression is just horror at being betrayed.He's gonna rip that guys arm off and laugh now, or if he does die, take every single Kuma with him.
[SPOILER - highlight to read]: I doubt Whitebeard is dead, the most powerful man in the world cannot be slain so easily, that was his own crewmate though, I am betting that was due to Doflamingo and his power.
Also [SPOILER - highlight to read]: Smoker is still standing! Sure he looks like hell and Boa doesn't have a scratch but still, man went toe-to-toe with her!!
and i love that Oda has randomly introduced a swordsman who can match Mihawk.
Also, I love just how much higher One Piece was able to push the HSQ in this arc then Naruto was in it's latest one. Very similar event, vastly different levels of execution.
[SPOILER - highlight to read]: So, it looks like Whitebeard is going to give one last stand, hopefully a fight against Sengoku, and then is going to die. Seems fitting, as he said, you can't be the strongest forever.
Holy f**k Roger musta had a strong crew. Especially since his opponant was only barely beaten by 2 admirals (well, 1 admiral and garp) and the guy had about 50 crews backing him up. And by the looks of things Roger was just using a pistol and sword.
And Luffy is screwed imo, unless he gets veeeery skilled with Haki very fast.