Sayid must be the most conflicted and enigmatic character on LOST.
I see his fate or life story being very much that of a 'righteous sword'. Sayid is the dark avenger, sometimes acting on his own, sometimes being used by others, but invariably acting to atone or correct transgressions in the world. As a child, he was criticized and ostracized by the little, rich girl he secretly adored, and by implication other children as well. Perhaps it was during those moments that he developed the need to take up for those that were unable to defend themselves, vowing that as he grew up, he would never allow people to take advantage of the innocent again.
As a young man he found himself in the Republican Guard where the wars in Iraq positioned him at the point in fighting terrorism and those who would harm the innocent.
On the island he falls prey to his violent reactions to perceived attacks on the weak by going after Sawyer. As a very ethical person, his own actions are distasteful to him, and yet he views them as necessary. He sometimes sees his own guilt and search for forgiveness and redemption in the eyes of his enemies and friends alike.
But his story remains powerfully consistent, and repetitive. He betrays his friend's trust at least partly to prevent innocent bloodshed. Ben takes advantage of the terrible death of his life long love (It is very unlikely that Widmore killed Nadia. Much more likely that Ben lied to Sayid to advance his own selfish agendas) to utilize Sayid's passionate talents. He kills the young Ben, and joins Faraday's potentially naive plan, all in an effort to correct transgressions against the O815 survivors.
Terrible events keep occurring in his life that put a deeply moral and conscientious man in the eye of the hurricane. Some people would shirk from the resultant hard decisions that must be faced. Sayid does not. He acts according to his conviction, even if it is abhorrent to him. But the resultant blood on his hands is a source of terrible guilt and self-loathing. He believes himself beyond redemption.
