To be specific, we learn that a man named Ulysses seems to want the Courier's head.
Now here's what I think about the Courier's path based off of Van Buren documents (the canceled FO3 project from Interplay before Bethesda acquired the rights to the Fallout series):
First and foremost, the protagonist of Van Buren was "The Prisoner" of Tibbets Facility. This location was also what originally was supposed to be the Big Empty, which we learned from Dead Money now is some high tech facility. Secondly, the name "Ulysses" also was in Van Buren but was changed to ODYSSEUS. ODYSSEUS was an advanced A.I. "ZAX" unit, much like President Eden from Fallout 3, or The Emperor from Fallout 2. ODYSSEUS's role in Van Buren was as the "warden" of Tibbets Facility.
Now then, I don't think that Ulysses is going to be the exact same, but based off of the Van Buren protagonist, the Van Buren version of Ulysses, "ODYSSEUS", and the fact that the Courier starts off his role from being shot in the head (where as every other protagonist has started based off of coming out of a vault, or from a village), I think the Courier may have killed someone very important to Ulysses; either intentionally or unitentionally. However that screwed Ulysses up so much that perhaps his moral compass is going off the deep end.
We see that he isn't a bad guy; he saved Christine and "gave her her mark", which set her on her mission to get vengeance on Father Elijah.
I also think Ulysses may play a part in the main storyline. While Benny delivered the [would be] killing blow to the Courier, we never truly discover how he figured out where the Courier would be heading. Perhaps Ulysses gave him that information, seeing as he told Nash to give you, Courier Six, the job to take the platinum chip.
Anyways, there's my thoughts. What about you guys? Why do you think Ulysses wants to fight the Courier, or at the very least meet him at the Divide? What do you think the Courier did that must've pissed him off that much?
