Episode 122

The Power of Banryu: Duel to the Death on Mt. Hakurei is the one hundred twenty-second episode of the InuYasha anime.

Synopsis

 * 1) Bankotsu destroys his thousandth yōkai, giving his Banryū its ultimate power.
 * 2) However, doing so caused Bankotsu's blade to emit a demonic aura, making him susceptible to Inuyasha's Bakuryūha, which Inuyasha uses, finally defeating the leader of the Shichinintai.

Summary
The battle between Inuyasha and Bankotsu heats up when Bankostu reveals he used the lives of 2000 humans and demons to make Banryu much stronger. After they punched each other for a bit, Inuyasha finally uses Backlash Wave on Banryu's demonic aura to defeat Bankotsu.