There is a trick to that. If you quit without saving and then restart your system and load your last save, it load to before you died.
I absolutely love achievements like that one, to finish a game without dying/taking damage or so I think the
from sonic 4 and the Untouchable achievements from Too Human are probably some of the most... fist pumping ones I've gotten just for pure focusing and trying to remember to breath out inbetween boss attacks :D Not sure if anyone other than me actually played Too Human before there was a law passed to destroy copies of it :D but damn good game once you get passed its flaws and yeah hard as nails, so finishing the whole game without a death, rockers hard.
Why not check me out on youtube and help me on the way to 2k subs over at www.youtube.com/stormcloudlive