Uchiha Sasuke
Level of Infection Displayed: Unactivated Seal
Orochimaru saw Sasuke as the next vessel to hold his soul. To that end he decided to grant Sasuke some of his power to determine the potential the young Uchiha possessed.
Level of Infection Displayed: Level One
When Sasuke participated in the Chuunin Exam in the Forest of Death, Orochimaru placed the cursed seal upon his neck by biting him. When he activates his Level 1 seal, the seal spreads in a raging, flame-like pattern.
Level of Infection Displayed: Level Two
After Sakon gave Sasuke the Seishingan drug, the Four Sounds placed Sasuke into a container which they then sealed with their powers. After ingesting the drug, Sasuke in a sense died and his body was able to forcefully grow accustomed to the Level 2 power. In his Level 2 state, Sasuke's hair greatly increases in length and he is able to extend wings from his back. In this form he is able to utilize a more powerful, dark Chidori.