Kid Buu is the original and purest form of Majin Buu; even though this form is the last one that he appears in. This Buu appeared after all of the fighters that he'd absorbed were removed from his system. This form is Majin Buu's strongest form as his previous forms are brought down in strength by the innocence of the Kais he had absorbed. Unlike his previous forms, this form of Buu's thought process is seen to be irrational and spontaneous, even destroying his own body to destroy the Earth.
Unlike his anime counterpart, in the manga series, this Buu is never seen to be capable of speech. The first form he appears in is actually the form that he took after he'd absorbed Grand Supreme Kai millions of years earlier. When inside Super Buu, Goku and Vegeta rip Good Buu out, causing Super Buu to revert to this form. Although he appears smaller than any other form, he is more dangerous and powerful than any other forms of Buu, due to his full relentless evil. He is also completely free of restraint, holding his own against Super Saiyan 3 Goku, Good Buu, and Super Saiyan 2 Vegeta. In this form he has no trace of sanity, and because of this is extremely volatile. He retains his childish personality, becoming amused and laughing hysterically at his own destruction of entire worlds. In addition, he is the final villain of Dragon Ball Z.