Originally Posted by Insaniac85
info for the hardcore-cheevo: there's a glitch in which you only have to play level 1-8 on hardcore. level 9 can be played on normal (maybe even casual).
also hardcore can be played in coop.
Thanks and I'll add that bit about the glitch. And yeah, I know it can be done in co-op but I think you'd be better off playing it solo. Also none of your experience will carry over for the "The Daily Grind" achievement if you play online.