Theoretically, you could get this trophy starting anywhere except the end of the game. It is somewhat misleading in that it doesn't specify whether it has to be done in one chapter or not.
Thankfully, you can do it over a series of chapters, it just has to be done in one sitting; no dying, no restarting, no quitting. If you do this on Very Easy, it's not the kills that are hard, but the random deaths from falling, or missing a ledge.
I did it by selecting Chapter 5, and playing through the level until the end. This continues to Chapter 6, at the chateau, where I unlocked the trophy during the fight in the second courtyard where you reunite with Sully. The only time I nearly died was losing my way when you have to dive through the underwater passage.
Another good level to attempt this on would be starting at Chapter 14, 'Cruisin' For A Bruisin' and continuing through until you unlock it.
Best of luck.