@Vukan-Vuk Yes, @CAP-33 is correct - you can not turn off the POWER LED of Power Dock without some hardware action / modification.

The expled tool - originally - is able to control the RGB LED of an Expansion Dock via GPIO15, 16, 17.
See also Expansion Dock > Using the Dock > Controlling the RGB LED

Power Dock 2 has a virtual PB (PushButton) that we can push with the power-dock2 utility via GPIO16 (or unintentionally because GPIO16 is floating by default ;-).
See also Checking the Battery Level

Up to now I thought that PB is effective only if a battery is connected to the board.
It seems you have found a creative way when you are keep pushing it with an expled command - theoretically 200 times per second ;-).

You should try to stop the PWM signal on GPIO16 with fast-gpio set-input 16 - this was the default state of GPIO16.

Notes to @Lazar-Demin
Software PWM on the Omega’s GPIOs

Using the Omega’s GPIOs > Fast-GPIO > Generating a PWM signal on a GPIO:

Generate a software-based Pulse Width Modulated (PWM) signal on a selected pin. Specify the desired duty cycle and frequency of the PWM signal.
fast-gpio pwm <gpio> <freq in Hz> <duty cycle percentage>
This will launch a background process that will generate the PWM signal.
To stop the PWM signal, set the GPIO’s value:
fast-gpio <gpio> 0

fast-gpio set <gpio> 0 - set the output LOW (if there's an active LOW LED then it will be ON) or
fast-gpio set <gpio> 1 - set the output HIGH (if there's an active LOW LED then it will be OFF).

# Omega2+ v0.2.2 b201 root@Omega-99A5:~# expled 0xf21133 Setting LEDs to: f21133 Duty: 6 94 80 root@Omega-99A5:~# ps | grep fast-gpio 4641 root 1160 S fast-gpio pwm 17 200 6 4644 root 1160 S fast-gpio pwm 16 200 94 4647 root 1160 S fast-gpio pwm 15 200 80 4761 root 1188 S grep fast-gpio

Are these fast-gpio pwm ... processes running in the background really?