Naruto Season 6 Episode 6

The intense chakra of Sasuke's Curse Mark 2 form, turns his Chidori into black lighting, called Habataku Chidori (Flapping 1000 Birds) respectively.

The mysterious ninja watching everything that is happening at the Final Valley is Zetsu, a member of Akatsuki.

In the English dub, the Valley of the End is named the Final Valley.

Original Airdate: May 11, 2005

Original Episode Title: The Worst Conclusion and the Rain of Tears
Romaji Episode Title: Namida ame no Ketsumatsu
Kanji Episode Title: 涙雨（なみだあめ）の結末

The place where Naruto and Sasuke are fighting is called the Valley of the End.

When Naruto's Rasengan clashed with Sasuke's Chidori, the vast amount of chakra caused a giant black orb to surround both of them

Sasuke's cursed seal transformation changes his hair and skin color, puts a cross on his face, and puts 2 hand-shaped wings on his back.

This is the first time Naruto uses Rasengan without making a shadow clone or using his other hand.

First appearence of another member of Akatsuki other than Itachi and Kisame. This one is Zetsu, from the Village of Hidden Grass. It is presumed he's a plant user.

Sasuke survives only because he had his forehead protector on.

First true appearance of an Akatsuki member since episode 85, a character named Zetsu.