Evil Buu

Evil Buu (魔人ブウ 純粋悪, Majin Bū Junsui Aku; lit. "Majin Boo Pure Evil") is a tall, thin, and gray emaciated form which appeared after Majin Buu dispelled the evil from his body. Evil Buu represents the dark side of Majin Buu and possesses the bulk of their power, a result of Majin Buu's anger becoming more than he could resist until he expelled it as Evil Buu.
This explains why his reaction to the shooting of Mr. Satan was so despicable, and even appalled the Fat Majin Buu. The Pure Evil Majin Buu is a polar opposite of the "good" Majin Buu in all aspects apart from apparel (except for him having a dark blue cape where Fat Buu has a purple cape), including the color of his flesh (a drab grey), his incredibly thin body, and gravelly manner of speech.
Once he emerges from the puff of smoke in the air after Buu expelled his inner evil, Evil Buu immediately proceeds to mercilessly eliminate crazed gunman Van Zant in the mountains with no mercy. He then battles against Majin Buu, with the evil incarnation quickly gaining the upper hand, the fat Buu unable to land a hit. After dominating the battle, he consumes "Good Majin Buu" after reflecting an attack meant to turn him into chocolate. Evil Buu then eats the chocolate Good Buu, causing them to re-fuse, this time with the evil on the outside instead of the inside, resulting in Super Buu. While transforming into Super Buu, he also uttered a maniacal laugh while steam was expelled from his body.



Information from:
http://dragonball.wikia.com/
Information picture :
http://tekilazo.deviantart.com/