Juugo

Juugo is the largest of the three members that comprise Sasuke Uchiha's new team, Snake (which is now Hawk). Juugo was being held at Orochimaru's North Base, which is also where most of Orochimaru's secret research was conducted. Suigetsu can't stand Juugo and comments that one of the reasons he had to retrieve Zabuza Momochi's sword was because of him. Karin notes that Juugo is mentally unstable, a view confirmed by images of Juugo muttering to himself over who he will kill next, which he determines by gender. Juugo is the means behind Orochimaru's development of the cursed seals. Sometime in the past, Juugo purposely sought out Orochimaru to cure him of his "impulses". Juugo has trouble controlling his rage, which unexpectedly causes him to transform into a berserk demon (much like a cursed seal does to its user). Upon examination, Orochimaru was able to isolate enzymes in Juugo's blood as the cause of this change.