Sasuke's Decision: Pushed to the Edge!

is episode 75 of the original Naruto anime.

Synopsis
Gaara began transforming into Shukaku, which dramatically increased his strength and speed, as well as the difficulty Sasuke faced fighting him. Sasuke used his Chidori to slice Gaara's arm off, but, at this pain, Gaara only became more determined to kill Sasuke. Unable to use the Chidori on his own anymore, Sasuke was forced to use his cursed seal so that he could attack Gaara with another Chidori. Again this failed to stop Gaara, and Sasuke collapsed due to the use of the Cursed Seal. As Gaara prepared to kill Sasuke, Naruto and Sakura finally arrived, and repelled Gaara.Gaara returned into his original form.