black blades:
-zoro can shoot 360 phoenix cannon like a bullet, i believe buggy can't survive that, he's only immune to cutting and slashing, i think brook can destroy him with his sword thrusts.
-that rust DF marine captain can be defeated with flying slashes.
-i'm assuming jozu's DF only hardens his skin, if that was the case then internal destruction haki can put him down.
now law on the other hand has a very useful awakening, if he can coat his entire body with KRoom it can turn him into a shock wave spamming ghost, immune to all kinds of damage, the only downside is the life threatening stamina drain.