Kat, Lightning, Raiden (MGS4/Revengence. I know at most he'd be DLC), Sephiroth, KOS-MOS, and/or Raziel.
I don't think many people hate KOS-MOS but not enough may know her or think she deserves it. Raziel seems fairly requested I suppose but still. Sephiroth probably wouldn't cause as much rage as say Lightning but I know there'd still be a bunch of whiners. --- http://z8.invisionfree.com/Final_Chase_Zone/index.php? PSN-Ragiroth