option a: he saves the world, has time to say goodbye to cortana, and then dies in a huge explosion, as the last spartan.
option b: he saves the world, but is to messed up. having his mission ended and about to die Miranda does him the favor by shooting in the head with a magnum. The shot cracks the overused helmet and we only get to see one eye and half a cryptic smile, before blood comes out and bam! credits
he never gets the girl, hes just too cool for a girl