Complex sentence: Before Windu is about to kill Palpatine, Anakin intervenes and disarms Windu, allowing Palpatine use his Force lightning on him, forcing him out of a window to his death.
Split into simpler sentences: Before Windu is about to kill Palpatine, Anakin intervenes and disarms Windu. Palpatine uses his Force lightning on Windu, forcing him out of a window to his death.