Every great hero needs an equally great villain. This is especially true in the Shonen series where the story is mostly about the force of good against the power of evil. Goku has Frieza, Naruto has Madara, Luffy has the World Government, and Bleach has one of the most charismatic and terrifying evil masterminds that ever grace this genre, the former Captain of the 5th Division in Gotei 13, Sousuke Aizen.