He is condemned for the massacre of his own clan, no one knows but he massacred the Uchiha and even killed his parents with his own hands to save the entire village and his younger brother of his own clan, he suffered a lot of mental torment, he Can use Sharingan and Mangekyou Sharingan (in Naruto anime), Itachi is very powerful, but usually has a relaxed and calm, thoughtful and cold. Konoha is also a kingdom,the king and queen want to execute Itachi, but the princess saves Itachi