Ensemble Dark Horse: Shoteka. Even though he's only appeared in the first two books and hasn't been seen since, he's easily the most popular antagonist.
Toklo's battle against Shoteka in Great Bear Lake. He's already a cub and fighting a big jackass bear who tried to kill him, and Toklo takes him down thanks to speed and his mother's spirit.
Nanulak getting his comeuppance at the end of Island of Shadows is just so satisfying.