Al Pacino was one of several actors considered for the part of John J. Rambo in the 1982 action-thriller First Blood, and his version would have been very different. The film adaptation of David Morrell’s 1972 novel of the same name, the leading Rambo role eventually went to Sylvester Stallone, who rewrote the screenplay to make the character more sympathetic. Had Al Pacino played John Rambo, however, the action hero would have differed greatly from Sylvester Stallone’s interpretation in a number of ways that are more faithful to David Morrell's original novel.

https://screenrant.com/rambo-first-blood-al-pacino-casting-change/