The Fifth Gate: A Splendid Ninja is Born

is episode 50 episode of the original Naruto anime.

Synopsis
Lee's speed proves too much for Gaara, and his sand is no longer able to form a shield fast enough to be of use. Lee opens the Fifth Gate and uses his most powerful attack, Reverse Lotus. Unfortunately for Lee, Gaara survives this final blow by softening his fall with sand and uses the sand to crush Lee's left arm and leg. Gaara moves his sand to finish Lee, but Guy jumps in to protect his student. Lee, though unconscious due to the pain, rises to continue the battle, his desire to win fueling his broken body. Guy cries for Lee's dedication, and Lee is taken away to recover. The medical ninja announce that Lee's injuries are too severe to be completely healed and that he will never be able to fight as a ninja again. Guy regrets teaching Lee such dangerous techniques, but vacates the ring for the final match between Choji Akimichi and Dosu Kinuta.