Nine (My Hero Academia) is the main antagonist of My Hero Academia: Heroes Rising.
Nine wanted to create a world where the strongest ruled making himself the king. To achieve his goal he donated his body to the League of Villains where he was given a copy of All for One's quirk allowing him to steal people's quirks.
However, he did not undergo the genetic modifications Tomura Shigaraki would later receive to store and utilize the stolen powers properly. Because of this, his already frail body became weaker and he was limited to only eight other quirks on top of his existing thunder quirk hence the name.