Many see Kakuzu not as someone hoarding money to spend, but as a control freak who needs to possess resources so they cannot be used against him.

His life is a story of a dutiful soldier turned into a soulless "Frankenstein" monster by the cold, unforgiving bureaucracy of the Shinobi world. If you want, I can: Rank his strength against other Akatsuki Detail his five elemental hearts Explain his partner Hidan's abilities Let me know how you'd like to narrow down the list. The Immortal Kakuzu: Anatomy of a Shinobi Villain

Originally, Kakuzu was an elite, loyal Jonin from the Hidden Waterfall Village (Takigakure). He was tasked with an impossible, near-suicidal mission: to assassinate Hashirama Senju, the First Hokage and "God of Shinobi".

When reanimated, Kakuzu's soul is described as returning to the afterlife with a calm demeanor, perhaps finally free from his long, angry life.