After you beat the game, go into the Treasures option and select the in-game movie. You don't have to watch the entire thing - just skip ahead to the point where Kratos is in Elysium.
Playing through the game and watching the scene counts as one viewing. If you go back through on hard and watch it again, that counts as two. Then you just need to go back and view it once more from the Treasures menu.
You could just go in and watch it twice to get the trophy out of the way after you beat the game the first time.