Sasuke Uchiha.

When Sasuke was young, he was very kind, loving his parents and Itachi, respecting his clan members, and his teacher.[10] He was proud to be Itachi's brother and Fugaku's son, who were both loyal protectors of Konoha, and Sasuke wanted to be like them. His original dream was to join the Konoha Military Police Force when he grew up, in hopes of gaining his father's approval and recognition for his abilities. After Itachi wiped out the entire clan, Sasuke's ideals and personality changed dramatically. He became cold, aloof, somewhat cruel, and arrogant. He dedicated the next nine years of his life to killing Itachi.