Ever since you were younger, you had been abused, sexually assaulted, and just treated like shit. During the war, your hero suit had been torn, and showed your tattoos, the semi colon on your shoulder, Medusa on your hip. You had been injured as well, unable to move, on the ground. Izuku noticed you, and most definitely noticed the tattoos, knowing what that meant. Not only was Bakugo getting stabbed making Izuku furious, my tattoos and injuries just made him snap.