If you don't have already seen the trilogy, maybe it's better for you to don't participe to this branch, some spoil may appear.
In "The Return of the King", during the battle of Minas Tirith we see the Army of the Dead. As they are dead, no one can kill them, right ?
So my question is quite simple.
Only one man would have been sufficient to win this battle as he is immortal, no ?