person with nothing left to lose; invincible person
Internet slang for a social outcast who feels they have nothing to lose, often used in discussions about crime or extreme behavior. The literal meaning 'invincible person' is secondary.
Online, crimes committed by people with nothing left to lose became a hot topic.
彼は社会から孤立して、無敵の人になってしまった。
He became isolated from society and turned into a person with nothing left to lose.
From 無敵 (invincible) + の + 人 (person). Coined on Japanese internet forums to describe individuals who, having lost social ties and prospects, feel they have nothing to lose and thus act without restraint.