Arbiter vs. Master Chief? Why? What about the whole Elite-Human truce?
Wha- Why? Why would an Elite, after helping a couple humans (who he attacked before) stop Halo, have any reason to want to fight Master Chief? I mean- it makes no sense.
If there HAD to be any kind of boss battle, it would be with either truth or gravemind (i dont know if he's good or evil, but in halo 2 it was obvious that there wasnt really much of a choice in him helping the humans and elites).