Tit for Tat

Eye for an Eye

When game theories tested different strategies of winning against others using computer algorithms, designed to compete in a game called "The Prisoner’s Dilemma" which gives two choices either to defect their opponent or to cooperate with your opponent, they eventually found the best strategy is the "Tit for Tat" when played for longer time period, out of multiple strategies submitted

Source: Veritasium (https://www.youtube.com/watch?v=mScpHTIi-kM)