{Spoiler: Armchair psychology}
I think Ted is a thoughtful and believable portrayal of a guy with borderline personality disorder and an abusive background. He doesn't believe anyone can truly care for him and that the only way he can survive is by using and manipulating others. His feelings of emptiness and loneliness are so intense that to escape them he feels justified in doing things he would consider horrible under other circumstances.
We see in several of the paths that Ted is capable of change. It is something of a revelation for him to discover that Daren and the others really care about Colin and Colin really cares about him. If Colin or his friends push him in the right ways, Ted is willing to give up his original plan and be more trusting and less selfish.