Who kills the Emperor in Return of the Jedi?

The story behind the answer

In the Death Star II throne room, as Luke is tortured by Force lightning, the armored Sith Lord turns on his master and hurls him into the reactor shaft, sacrificing himself in the process. Luke doesn’t deliver the fatal blow—he rejects the dark side and refuses to kill. Leia is on the Endor strike team and never reaches the throne room. Boba Fett isn’t even on the Death Star; he fell into the Sarlacc earlier on Tatooine.

This act completes Anakin Skywalker’s redemption arc and fulfills the “Chosen One” prophecy to bring balance to the Force by ending the Sith’s Rule of Two. The lethal surge of lightning damages his life-support systems, leading to his death shortly after he reconciles with his son.