Darth Vader dies in Return of the Jedi primarily because he is mortally wounded while saving his son, Luke Skywalker, from Emperor Palpatine's Force lightning. During the Emperor's attack on Luke, Vader intervenes by throwing Palpatine down a reactor shaft, but the intense Force lightning fatally damages Vader's life-supporting suit and severely injures his body. This damage, combined with his already fragile condition from previous injuries sustained earlier in his life, leads to his death shortly afterward

. More specifically, the Emperor's Force lightning causes critical failure in Vader's life-support systems, particularly affecting his breathing apparatus, which he depends on due to his cybernetic enhancements. Medical analyses suggest that Vader likely died from respiratory failure caused by the damage to his suit and body

. Additionally, some interpretations suggest that Vader's survival had been sustained by his hatred and connection to the dark side, and once he turned back to the Light Side by saving Luke and killing the Emperor, that life- sustaining hatred dissipated, contributing to his death

. Before dying, Vader asks Luke to remove his helmet so he can see his son with his own eyes, symbolizing his redemption as Anakin Skywalker. He dies peacefully after this moment of reconciliation and is later cremated by Luke on Endor. His spirit appears as a Force ghost alongside Obi-Wan Kenobi and Yoda, marking his return to the Light Side