Sophocles isn't simply saying injustice is bad—he's making the bolder claim that it surpasses all other wrongs in its corrupting power. A person might commit theft or violence in a moment of passion and later feel remorse, but injustice is a systematic betrayal of one's own sense of rightness, a wound inflicted knowingly. Consider a judge who accepts a bribe: she hasn't merely stolen money, she's dismantled the entire machinery by which others might trust fairness itself, poisoning the very ground on which society stands. That's why Sophocles ranks it above all other failings—injustice doesn't just harm its victim; it poisons the soul of the one who commits it.