Eye to Eye: Sharingan vs. Sharingan!

is episode 82 of the original Naruto anime.

Synopsis
Kakashi and Itachi exchange blows, each being very proficient with the Sharingan. Itachi, however, is more so, and quickly attacks Kakashi with his Tsukuyomi. As Kakashi struggles to remain standing, he asks Itachi why he's returned to Konoha. Itachi replies that they're after Naruto, which Kakashi elaborates as meaning they want the Nine-Tailed Demon Fox for their organisation Akatsuki. Angered that Kakashi knows of their organisation, Itachi instructs Kisame to kill Asuma and Kurenai, but to bring Kakashi with him. Before Kisame can do so, Might Guy arrives, forcing the two to flee.

Trivia

 * Kakashi did not have his scar at the instant after Might Guy saved him.