Well, I personally didn't like Orochimaru's first or second deaths, but I always knew we hadn't seen the last of him... and I was right, of course. We'll see what happens when he comes back for the Boruto movie. As for my other favorites, Madara and Itachi, I liked both of their deaths, Madara's especially. The Black Zetsu thing was eh, sure, but his talk with Hashirama was excellently done.
Sasori had a cool fight and died, which was fine, and Toneri didn't die.
... Sorry, I can't choose just one favorite.