For me it's gotta be the sensui arc and the phantom troupe arc. Chimera arc was great but 60 episodes and about 30 of them were dragged out for no reason it made no sense. How about you guys
Yuyu is my fave old anime, I cant seem to pick an arc as a whole, I like the final arc in the demon world. other than that, I enjoyed the first appearance of the Jin and Toya. It's my favorite team arena battle overall