I only played the good side, but I observed that the Outsider is a neutral party. He merely watches people who change things. On occasions he grants those he watches power, but it's up to the individual to choose how they'll use it.
In the end, he's just a dumb whale watching the world react to him.
Dishonored asks a question; How will you conduct yourself? Will you kill to get what you want, or will your actions?
A outsider isn't a supreme being, nor is "The Outsider".
He, if it is a He, is just a magical whale that observes the lives of humans. The Outsider is powerful, and occasionally intervenes in the lives he observes, but he is a neutral party when it comes to morality.
He listens to the stories of peoples lives, rarely empowering them.
If he is to be viewed as a deity, it certainly isn't as a moral deity. As he often hands the malicious tools of destruction.
To summarize; the outsider is a magic whale, it watches people with influential lives, and it rarely bestows magical power to others. Need I remind you of those blasted Overseers and their song?