Majin Android 21

In her true form, Android 21 keeps her curvy body, her skin turns pink, her hair becomes white with a pink tint, her ears become pointed, her eyes changing depending on if her evil half takes over, and she gains a tail. Her attire changes to a black tube top, keeping the black arm sleeves with gold bracelets at the ends, her boots become black, and also gaining white baggy pants. It's noted that she most resembles a Majin in this form. Her eyes slightly vary depending on which moral alignment she represents. In her good representation, she retains the eyes from her human form. In her evil representation, her eyes instead are more similar overall to that of a Majin.

Her appearance in her true form is the result of her having all of the traits of the Z Fighters, Frieza, Cell and Majin Buu rolled into one.

Her hunger is so great and painful that it has led to Android 21's psyche being damaged and manifesting a split personality. The longer she goes without feeding, the more the evil side of her gains control. When her true persona is in control she acts like a kind and motherly woman who was concerned about Android 18 and agreed to help her. When her evil persona is in control, however, she becomes a sadistic and power-hungry sociopath, wanting to "devour" all the powerful fighters, drawing to the point of near insanity. Her gluttonous lust for "devouring" powerful fighters is similar to the traits of the Majins, inherited when Buu's cells were added to her. Her good side is friendly towards Good Buu presumably due to their shared biology and love of sweets.