Fayol's principle of equity emphasizes the fair treatment of all employees, suggesting that they should be treated with kindness and justice. Based on this principle, the technique of Scientific Management that violates this principle is:

Differential Piece wage System

The differential piece wage system involves paying different rates for the same type of work to different workers based on their efficiency. This can lead to feelings of inequality among employees performing the same tasks, ultimately violating the principle of equity, which emphasizes fair treatment for all employees.