Refer to figure.
The tail rotor serves a vital role in a helicopter's flight dynamics. It provides a force that, when applied at a significant distance from the rotor hub, creates a moment capable of balancing the torque reaction generated by the fuselage in response to the main rotor's rotation. This critical function prevents the helicopter from unwanted rotation in the opposite direction of the main rotor.

Furthermore, the tail rotor is the primary means of controlling the helicopter's yaw, or its rotation about the vertical axis. By adjusting the thrust produced by the tail rotor, the pilot can effectively steer the helicopter.

The main rotor generates torque that naturally opposes its own rotation direction. To counteract this torque and maintain stability, the tail rotor must exert thrust in the same direction as the main rotor's rotation.

During a turn in the same direction as the main rotor's rotation, the torque generated by both the main rotor and the turn itself intensifies. As a result, the tail rotor must work harder to counteract this combined torque, leading to increased power requirements.

Conversely, when the helicopter turns in the opposite direction of the main rotor's rotation, the main rotor's torque aids the tail rotor in countering the turn. This reduces the tail rotor's workload, resulting in decreased power demands because it doesn't need to exert as much force to maintain control.

Looking at the power curve attached you can see the green line going from the power available line downwards with increasing in speed. This represents the maximum power required for a hover out of ground effect (OGE), adding to this by turning in the same direction as the main rotor will increase the power demand from the engine because more thrust is needed by the helicopter to turn. Therefore, the hisghest power requirement will be hover OGE with a pedal turn in the direction of the rotor spining.