I think the slave route, which I didn't know about for the longest time, because it requires you to ignore the common sense decisions in the prologue.
I'm not sure which slave route I like better, as there is a branching point if you kill the khan's messenger or let him leave.
I've currently exploring both slave routes, but another decision point is currently stalled on the route where you kill the messenger, and the route where you leave the messenger alive has not been touched for a while.
Like wise if you answer the khan truthfully rather then lying there is yet another option for the slave route.
I love this game, but I'm going to probably fill up a terrabyte of saves with all the branching choices.