The penultimate battle between Shira and Manji. Magatsu and Tanpopo join in
Shira is a complete maniac, but give the bastard his due. In addition to totally outfoxing Manji at the beginning of the climax, he continues to show his dominance even as Magatsu (and eventually Meguro) join the fray. The very fact that he was able to hold his own against two of the series' recurring Badasses (and a passable Action Girl) at once merits him some serious cred.
It may be a bit cruel, but I guess in a series full of pretty graphic fighting scenes, Shira's demise definitely is worth mentioning. He is almost cut in half lengthways and then systematically dismembered by the heroes, until he can move hardly more than his mouth. Then he is devoured by wolves. And, thanks to the Kessen-chu, still alive to witness it. As if that wasn't enough, the bastard actually seems to kinda enjoy it. A fitting end for one of the most iconic monstrosities in the history of seinen manga.