Spoiler alert (124+)
Naraku's twist was that he gained a new body and offed kikyo with it, and even manged to drive sesshomaru back (note: sesshomaru is almost like hiko seijeru of Inuyasha, you don't mess with him and live afterwards...), so he obviously gained some new awsome strentgh...
the new bad guy is hakudoushi, who is another deattachment of Naraku, but unlike others, this one seems to be smarter, stronger and better, from what i understood, he is the left overs from naraku's human part, or something like that...
anyway, he's evil, he's strong, and he survived quite a few encounters with inuyasha without getting his ass totally kicked around like a french school girl...
the thing with him is that he seems to have his own ajenda within Naraku's one, and he isn't an ordinary subordinate, but a "Boss" on his own accord.
by the way, does anyone know why in the anime Inuyasha killed bankatsu with his banaryu and in the manga it was just the usual thing?