Highlander II: The Quickening (1991)

In 1999, Professor Allan Neyman and Connor MacLeod develop a shield to protect Earth from the radiation caused by the damage in the ozone layer. Twenty-five years later, Earth is dying due to the effects of the shield and the terrorist group commanded by Louise Marcus is trying to destroy the shield. In flashback, it is explained that MacLeod and his friend Juan Sánchez Villa-Lobos Ramírez are aliens from the planet Zeist expelled from their planet by the tyrant Katan (Michael Ironside) that decides to kill MacLeod.