In case anyone was wondering, you cannot get this trophy by using back-ups on your USB. I have gone through this game by backing up before every difficult part and deleting my save file every time I died. It took me 2 precious hours
to find this out the hard way.
Now before people start calling me a moreon for overseeing the trophy description saying that it has to be done "in one sitting", I was aware of that but found the meaning of "one sitting" to be ambiguous. Several people have stated that you can't get the trophy through chapter select, but nobody mentioned quitting to the xmb and just resuming the game. By the way, somebody on the related forum on xbox360achievements.org mentioned another game that required one sitting that could be done with usb back-ups. But now I have confirmed it,
it does not work on this game.
It was some good practice, though. I now knew every nasty detail that I could expect. I restarted the game and quit after dying a fourth time, being not even halfway through. (Mistakes: 1st: hit by the 2 swinging traps on a rope in the tree house, 2nd: falling in the mud because I had pressed X twice so I grabbed the solid part and let loose again, 3rd: drowned because I jumped away from a rotten sinking crate too late, 4th: probably so stupid that I can't remember.) I restarted again and quit after falling in the hole while jumping away from the spider as a mummy.
Finally, I restarted again and managed to stay concentrated, ending the game with 3 deaths.
1st: the crusher on the conveyor belt, I tried to hang on the side but climbed up by accident and got crushed
2nd: crushed between a large block and the ceiling between the parts with the last 2 machine guns
3rd: the very last trap before hitting the windscreen, luckily I had not lost 5 lives before that point or I would have gone mad
My hands were shaking terribly while going through the last chapters