Q:

I dropped brigthness to 0 in compizconfig. How to recover

I was testing the brightness, opacity and saturation plugin and dropped the brigthness to 0, now without having apply (but pressed ESC), I can´t control my Ubuntu anymore (all windows are black). How can I recover from this?

A:

Press Ctrl + Alt + F1 to go to TTY mode, type your user name and password. Then run following command to restore compiz setting.
rm  -rf ~/.compiz-1 ~/.config/compiz-1

To access GUI again, press Ctrl + Alt + F7

