This is the relevant information: The title is a reference to the Four Horsemen of the Apocalypse, as the rider of a pale horse is Death.
This justifies what answer for what question? Q & A:
Passage: Pale Rider is a 1985 American western film produced and directed by Clint Eastwood, who also stars in the lead role. The title is a reference to the Four Horsemen of the Apocalypse, as the rider of a pale horse is Death. The film, which took in nearly $41 million at the box office, became the highest grossing Western of the 1980s.

Question: Based on this passage, who was the pale rider supposed to be?
Death