I've killed off a lot of characters in many of my stories, plenty of times I killed characters by the boatload, but I've gotten more sparing with how I kill off characters. For a lot of the characters I kill off it's because it's an inevitability of their character arc or because sh*t happens(rarely enough to be a surprise). If it fits Chief's journey I'm all for it and after the end of Halo 4 I could see it happening because all of the things he has seen and done seem to have a large toll. But it has to be a good send off. I'd personally give him a send off similar to Spartacus. However I would have him finish the fight before he dies from his wounds. It simply seems like a fitting send off for him. I realize he's a gaming icon but sometimes I've wished some of my favorite characters died earlier because it seemed more fitting and their eventual fates were disappointing.