Altair was born into the Creed, like many others. And, like so many others, he was unable to leave it. Assassins born into the Brotherhood stayed in the Brotherhood, for Al Mualim was a man protective of his secrets.
The bodies of deserters were often never found.
They waged an open war against sowers of violence and discord; the Templars acting as their main adversary. Yet Altair does not hate them, at first. Disrespect them for their misguided beliefs? Yes. But he does not hate them until their blades have claimed his own, people that he knew and (sometimes) loved. And so he kills them, in Jerusalem, in Acre, in Damascus. The who and the where do not matter, only the hunt.
At first he is appalled by the conditions of the Innocents whom he must protect. Relatively sheltered in the incense smokey halls of Maysaf, he is unprepared for the streets of the metropolis. Filled with thieves, brutal crusaders, shunned lepers and other wretches the people immediately evoke the pity of the young Assassin. He is blind to their searing, mistrusting glances and disapproving mutterings as he passes by. It is only years later that he comes to despise them for it. No matter what he does, the people are oblivious to the good that he is doing them. They hide away from him in fear as the Assassin slashes through mission after mission, none of it seeming to have any effect other than providing the washers at Maysaf with a constant supply of bloodied robes.
Adha was the final straw. Her death, though hard to bear, was made impossible by his own brethren. Every morning after for many months brought with it a 'How are you doing Altair?', 'How are you coping?', or a 'Altair, I'm so sorry for your loss'. Lies. Everyone knew that Assassins couldn't love, it was against policy. If anything, they were glad she was gone, a distraction from work removed. Adha was dead, she wasn't coming back, and Altair couldn't stand it and these betrayers were here spewing their poison all about him. So Altair did the only thing he could do; the only thing he knew how to do. He froze that rage into a cold controlled fury and threw himself into his work; accumulating bitterness and the filth of humanity and blood on his hands. Until, a few years later he stood with his fellows under Jerusalem, listening to Malik preaching to him about following the Creed.
And, opening his mouth, he replied with perfect conviction, "My way is better".
AN: Ah, it's another one about Altair! This isn't exactly expressing what I think. After all, Al Mualim is the only real Assassin who I would call a "traitor". However, there are some MEAN and jerkish Assassins in the Brotherhood. And, look at things from Altair's perspective. He probably didn't have much of a choice about becoming an Assassin, he has to protect people who are scared shitless of him, and open relationships/ affection aren't really promoted. Being bitter, I can understand.
...So yeah. If anyone has a particular prompt that they want me to write about, go ahead and leave a comment. Actually, please leave a comment anyways, I would love to know what you think!