If needed, a circuit similar to the crowbar is used to dissipate excess energy - see file. In the servo or motor drive world it's called a dynamic brake. It detects when the DC bus voltage to the output stage is higher than a predefined threshold and connects a power resistor across the DC bus to reduce the voltage. When the voltage is lower than the threshold, the resistor is disconnected.
The error amplifier tries to minimize the error regardless of the load whether it is resistive, reactive, complex, open circuit or zero ohms. The power factor should not matter providing the voltage and current are within the V-I limits of the output stage. Unlike a linear power output stage, a properly designed PWM output stage can drive virtually any load within its operating range. This usually means there are inductors in series with the output connections to limit peak current. These inductors can also be part of the LC output filter if needed to reduce PWM switching artifacts.